Surface areas and volumes exercise, 00:00 ( Introduction, and formulas of surface areas and volumes) 16:40 (Exercise 12.1 ,Q 1) 28:02 (exercise 12.1, Q 2) 37:55 (exercise 12.1, Q 3) 51:50 (exercise 12.1, Q 4) 1:01:31 (exercise 12.1, Q 5) 1:12:46 (exercise 12.1, Q 6) 1:21:42 (exercise 12.1, Q 7) 1:29:40 (exercise 12.1, Q 8) 1:43:26 (exercise 12.1, Q 9)