You can put this solution on YOUR website!
The formula for the volume of a square based pyramid is: (1/3)(b^2)(h) OR (b^2)(h)/3
You square root the base as its a square and there both the same
So it will be:= 1/3 x 3.5^2 x 4
= 16.3 ft cubic
Let me know if that helps, or if you want me to go over it?