$\cos ^{-1} \bigg(\large\frac{y}{b} \bigg)$$=2 \log \bigg(\large\frac{x}{2}\bigg),$$ x > 0=>x^2 \large\frac{d^2y}{dx^2}$$+x \large\frac{dy}{dx}=$

Question

\[(a)\;4y \quad (b)\;-4y \quad (c)\;0 \quad (d)\;-8y \]