Fewer combinations are possible. The only allowable options are as follows (as ordered pairs, where x is the number of 15 foot floats and y is the number of 30 foot floats): (0,4), (1,3), (2,3), (3,2), (4,2), (5,1), and (6,1).
Work Step by Step
$300x+600y \leq2500$ now is a constraint on the solution set. The graph shows the impact of this constraint. (The orange line is this inequality.)