a.) 25cm²
Reason: the base is a square, and squares have congruent sides. The area formula for a square is L•W, and since squares have congruent sides, we can simplify this formula into S•S or S².
b.) Correct
c.) Correct
d.) 64cm²
Reason: we already know that the surface area of the 4 lateral sides is 39cm². We also know that the square base is 25cm². Since the surface area is the total area needed to form the figure, we can add 39 and 25, which gets us 64cm².