If the points (1,1) and (3,5) were to be on the opposite side of the line $3x-5y+a=0$.Find the value of a?

Question

$\begin{array}{1 1}(a)\;a > 2,a < 16\\(b)\;a < 2,a < 15\\(c)\;a > 3,a < 5\\(d)\;a > 5,a < 2\end{array}$