Volume = Base Area x Height
The base is a square, the Square Area is given by:
Area = Length^2 (Any side measure, because all the sides have the same measure)
So:
-> Square Area = 15^2
-> Square Area = 225 in^2
Square Area = Base Area (Ba) = 225 in^2
Height = 16 in (The right angle formed between the line and base indicates that)
-> V = Ba x Height
-> V = 225 in^2 x 16 in
-> V = 3600 in^3