Student: ? 370 860 1550 2440 3530
Options:
(A) 900
(B) 840
(C) 750
(D) 860
(E) 80.
Another student: Let's say, hmmm...
10^2 - 20 = 80
20^2 - 30 = 370
30^2 - 40 = 860
40^2 - 50 = 1550
50^2 - 60 = 2440
60^2 - 70 = 3530. Final answer: (E).