(a) Two items are selected at random from four items labelled (p, q, r, s).

(i) List the sample space if sampling is done (1) with replacement ; (2) without replacement.

(ii) Find the probability that r is at least one of the two objects selected : (1) in a(i)1 ; (2) in a(i)2.

(b) How many whole numbers from 100 to 999 are divisible by (i) 4 ; (ii) both 3 and 4?