For which set of probabilities would events a and b be independent?
a) p(a) = 0.20; p(b) = 0.20; p(a and b) = 0.4
b) p(a) = 0.08; p(b) = 0.40; p(a and b) = 0.20
c) p(a) = 0.16; p(b) = 0.24; p(a and b) = 0.08
d) p(a) = 0.30; p(b) = 0.20; p(a and b) = 0.06