On a Tropical Island There Are 100 Potential Boat Builders

On a tropical island there are 100 potential boat builders, numbered 1 through 100.Each can build up to 16 boats a year, but anyone who goes into the boatbuilding business has to pay a fixed cost of $15.Marginal costs differ from person to person.Where y denotes the number of boats built per year, boat builder 1 has a total cost function c(y) = 15 + y.Boat builder 2 has a total cost function c(y) =15 +2y, and more generally, for each i, from 1 to 100, boat builder i has a cost function c(y) = 15 + iy.If the price of boats is 40, how many boats will be built per year?

A) 624
B) 200
C) 936
D) 400
E) Any number between 640 and 656 is possible.