Answer:
Below in bold.
Explanation:
(a) The surface area consists of the sum of the area of 3 sets of 2 congruent rectangles. The 2 rectangles are on opposite sides of the solid.
= 2(15*15) + 2(5*15) + 2(5&15)
= 450 + 150 + 150
= 750 unit^2.
(b). Similarly to the above:
Surface area = 2(12*6) + 2(4*12) + 2(4*6)
= 144 + 96 + 48
= 288 unit^2.
(c) Again:
Surface area = 2(25*16) + 2(25*16) + 2(16*16)
= 400 + 400 + 256
= 1056 unit^2.