(c) 4950 cm2
Area of the cake to be frosted
= Area of tops of (cuboid A + cuboid B + cuboid C) + Area of four sides of (cuboid A + cuboid B + cuboid C)
= (152 + 302+ 452) cm2 + [2(15 × 5 + 15 × 5)] + [2 (30 × 5 + 30 × 5)] + [2(45 × 5 + 45 × 5 )] = (225 + 900 + 2025) cm2 + (300 + 600 + 900) cm2 = 4950 cm2.