It is pretty simple, as equations go. England have to bat out 98 overs on day five to win this series 1-0 and go third in the ICC Test rankings.
They should do it, too, if teams assume the characteristics of their captain. Alastair Cook has the patience to battle all day, while Adam Lyth, Gary Ballance and Ian Bell are either playing for their places or their positions in England's batting order.
Cook has the motive as well: to restore order before the Ashes, after England in this second Test descended at times into anarchy in the field.
In the 16 overs yesterday before Brendon McCullum's declaration, New Zealand were bound to attack, yet England conceded not only 116 runs but any pretension to being the better side in this match.
New Zealand, for their part, will have two new balls in their attempt to force their fifth Test win in England, provided the rain stays away, as it failed to do on day four when 67 overs were lost. But they have only three pace bowlers and an offspinner to use them, so Trent Boult and Tim Southee will be tired before the time comes for a coup de grace with the second ball.
The anarchy has been caused by the 'Lord of Misrule'. At holidays in ancient Rome, a Lord of Misrule took control as the normal social order was turned upside down, temporarily, and masters served their slaves.
Here, England's Lord of Misrule has been Stuart Broad. The normal order has been turned upside down. The tail has wagged the dog - or rather the tail-enders in England's team, notably Broad, have wagged Cook the captain.
Allowances have to be made: bats have ever bigger and meatier middles; Headingley has a fast outfield thanks to new drainage; the square is a saucer, so the ball goes down a slope to the boundary in all directions; and England's slip-catching is ropy. Still, England have never conceded more runs per over in a Test than they have here. New Zealand, over their two innings, have been allowed to thrash away at 4.9 runs per over.
England's previous record was 4.6 an over in 1976 at Headingley. But that was mildly forgivable as the West Indian batting consisted of Roy Fredericks, Gordon Greenidge, Viv Richards, Lawrence Rowe, Clive Lloyd and Collis King. Even New Zealand would admit that is a cut above Tom Latham and Co.
Broad himself finished with the third-most expensive runs-per-over analysis for England, behind James Anderson and Bob Willis, of those who have bowled 20 overs in a Test: 33.1-1-203-7 or 6.12 runs per over. But James Anderson was in his youth at the time, and Willis at the end of his career (although every day for him was a bad-hair day), while Broad at 28 should be in his prime.
Broad could argue that his tactic of bowling bouncers at tail-enders, mostly from round the wicket, worked: no bowler in Test history has averaged seven wickets per game.
But this is a case of statistics being used to prove anything. It is far closer to the point that when Broad, armed with a ball less than 12 overs old, bowled to Southee with two slips, an extra-cover and everybody else spread around the boundary, it looked terrible. It looked like an army in retreat. It looked like anarchy. It was anarchy as Broad conceded 20 runs from one over then 19 off his next but one.
It looks bad as well as terrible. At first slip, too far away to communicate with Broad, Cook sees his captaincy dismissed as an irrelevance. Andrew Strauss would run to speak to his bowler about Plan B.
Cook, more passive, resigns himself to letting Broad do what he wants.
There is the moral effect, too, when eight opponents hit a six, the most in any Test innings, including Bradley-John Watling, who took his overnight 100 not out to 120. Matt Henry, at No?10 in his second Test, sees that England's opening bowler has given up any hope of bowling him or pinning him lbw on a pitch where the occasional ball does a lot. Knowing exactly what is coming, Henry mows two of the four balls he receives for six and feels a million dollars.
This is surely the biggest problem which Trevor Bayliss is going to face when he takes over as head coach. Cook, Broad, Anderson and the coaching staff agree a bowling tactic. Then the opposition play a few shots and everything flies out of the window.
One complicating factor is seniority. Cook came into the England team after Anderson, and in the same year as Broad. But the whip has to be cracked, and order restored. Otherwise a few hits from Australia's David Warner will be sufficient to put England to flight.