(1/2) (200 ft) (0 + 2 *520 + 2 * 800 ft + . . .+2*860 ft + 0)
= 1,332,000 ft^2
Average depth of 20 ft =
1,332,400 / 20 = 2,664,000 ft^3
2,664,000 ft^3 / 1 fish/1,000 ft^3 = 26,640 fishes
26,640 x 75 % = 19,980 catchable fishes
19,980 /20 = 999 licenses
hope this helps