Solid 1: Volume = 11 * 5 * 7 = 385 cubic inches. This is less than 400 cubic inches so can't be used.
Solid 2: Volume = 10*10*14 /3 = 466.67
Surface area = 397.32 sq. in.
Cost: 397.32 sq. in. x 0.02 = $7.95
Solid 3: Volume = Pi x 5^2 x 7 = 549.78 cubic inches.
Surface area = 376.99 sq. inches.
Cost = 376.99 x 0.02 = $7.54
Solid 4: Volume = Pi x 5^2 x 15/3 = 392.7 cubic inches. This is less than 400 so can't be used.
Solid 5: Volume = 4/3 Pi x 5^3 = 523.6 cubic inches.
Surface area: 314.16 cubic inches.
Cost: 314.16 x 0.02 = $6.28
unit cost:
Solid 2: 7.95 / 466.67 = $0.017 per cubic inch.
Solid 3: 7.54 / 549.78 = $0.014 per cubic inch.
Solid 5: 6.28 / 523.6 = $0.012 per cubic inch.
Solid 5 is the best option.
