Aand b are two events. let p(a)=0.5 , p(b)=0.9 and p(a and b)=0.15 . which statement is true? a and b are independent events because p(a|b)=p(b) and p(b|a)=p(a) . a and b are not independent events because p(a|b)=p(a) and p(b|a)=p(b) . a and b are not independent events because p(a|b)≠p(a) . a and b are not independent events because p(a|b)=p(b) and p(b|a)=p(a) .