If the system of linear equations given below has infinitely many number of solutions, find the value of $\large\frac{a}{b}$$\;-\;4$<br>$\qquad \qquad \qquad 2x\;-\;(a-4)y\;=\;2b\;+\;1,$<br> $\qquad \qquad \qquad 4x\;-\;(a-1)y\;=\;5b\;-\;1$

Question

$\begin{array}{1 1} a)\; \large\frac{5}{3} \\ b)\;\large\frac{3}{5}\\ c)\; \large\frac{-5}{3} \\ d)\; \large\frac{-3}{5} \end{array}$