What is the volume of the solid figure?

The solid shape is made up of two rectangular prisms. The first rectangular prism has a height of 10 inches, length of 5 inches, width of 5 inches and with connecting to the second rectangular prism, has a smaller height of 5 inches. The second rectangular prism has a length of 15 inches, height of 5 inches, width of 5 inches. The total length of the solid is 20 inches.

A.
625 in3

B.
750 in3

C.
800 in3

D.
1,250 in3