Safe Sex

What is the minimum number of condoms required for safe sex in each case:

(a) two men with two women
(b) one man with three women or three men with one woman
(c) three men with each other
(d) 2k+1 men with one woman
(e) m men and n women

If only I had been lucky enough in my bach-ing days to find this information useful. If you want the answers, go here.