\(M \propto N \) ; \(M \propto \frac{1}{\sqrt{P}}\). \(\therefore M \propto \frac{N}{\sqrt{P}}\) \(M = \frac{k N}{\sqrt{P}}\) when M = 3, N = 5 and P = 25; \(3 = \frac{5k}{\sqrt{25}}\) \(k = 3\) \(M = \frac{3N}{\sqrt{P}}\) when M = 2 and N = 6, \(2 = \frac{3(6)}{\sqrt{P}} \implies \sqrt{P} = \frac{18}{2}\) \(\sqrt{P} = 9 \implies P = 9^2\) P = 81