Ok so first you need is to identify all the factors of this equation.
The Rectangles Volume is the first you need to find.
9 feet x 16 feet x 4 in
9 x 16 x 4/12 which 4/12 can be converted to 1/3
V = 9 x 16 x 1/3
V = 48 feet cubed
1 yard = 27 feet cubed
48/27 = 1.78 yards cubed
Multiply 1.78 x 25 = $44.50