If the system of linear equations below has infinitely many number of solutions, find the value of $c$ .<br> $\qquad \qquad 6x-3y=-3 \\ \qquad \qquad\large\frac{x}{2}-\frac{y}{4}=c$

Question

$\begin{array}{1 1} a)\;4 \\ b)\;-4 \\ c)\;\large\frac{1}{4} \\ d)\;\large\frac{-1}{4} \end{array} $