If X has a binomial distribution , B(n , p) with parameters n and p such that P(X=2)=P(X=3) , then E(x) , the mean of variable X , is

Question

$(a)\;2 - p\qquad(b)\;3 -p\qquad(c)\;\large\frac{p}{2} \qquad(d)\;\large\frac{p}{3}$