Let $f$ be a differentiable function such that $f'(x) = 7 - \dfrac{3}{4}\,\dfrac{f(x)}{x}$, for $x>0$, and $f(1)\neq 4$. Then $\displaystyle \lim_{x\to 0} x\,f\!\left(\dfrac{1}{x}\right)$ equals: