In the pair E : 15 the number is the total of every whole number from 1 up to the place of the letter — E is the 5th letter, and 1 + 2 + 3 + 4 + 5 = 15. Complete the analogy: H : ?

H is the 8th letter, so the total wanted is 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36. The trap 28 stops the adding at 7 and 45 runs it on to 9. 40 is $8\times 5$, the place of H multiplied by the place of E, taken instead of a running total.