Tolong dijawab, dan jangan asal-asalan​

a. Vol = (1/3) × (22/7) × (10,5/2)² × 20 + (22/7) × (7/2)² × 4

= (1/3) × (22/7) × (21/4)² × 20 + 22 × 7

= 11 × (21/2) × 5 + 154

= 55 × 10,5 + 154

= 577,5 + 154

= 731,5

b. Vol = πr²t

731,5 = (22/7) × (21/4)² × t

731,5 = 11 × (3/2) × (21/4) × t

731,5 = (693/8) t

731,5 × (8/693) = t

8,4444….8 = t

8,5 ≈ t