Two events E and F are independent.If $P(E)=0.3,P(E\cup F)=0.5$,then P(E|F) - P(F|E) equals

Question

$\begin{array}{1 1}(A)\;\frac{2}{7}\quad(B)\;\frac{3}{35}\quad(C)\;\frac{1}{70}\quad(D)\;\frac{1}{7}\end{array}$