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# If $\phi (x) =f(x) g(x),$ where $f'(x) g'(x) =c$ and $\large\frac {\phi ''}{\phi} =\frac {f''}{f} +\frac{g''}{g}+\frac{Kc}{fg}$ then value of K.

$(a)\;1 \\ (b)\;0 \\ (c)\;2 \\ (d)\;-1$