a) 16 men were at work demolishing an old factory when part of it collapsed, injuring 3 of them. Three of the men were apprenticies

Calculate the probability that all 3 men were apprenticies??

b) Out of 40 paving slabs, 12 have internal cracks.

Determine the probability that, in choosing 5 slabs at random, a cracked slab is not selected….

answers for a is 1/560

b = 105/703

but how??