JEE Math Practice Question

Let f be a differentiable function such that f '(x) = 7 - $${3 \over 4}{{f\left( x \right)} \over x},$$ (x > 0) and f(1) $$ \ne $$ 4. Then $$\mathop {\lim }\limits_{x \to 0'} \,$$ xf$$\left( {{1 \over x}} \right)$$ :

1. A.does not exist
2. B.exists and equals $${4 \over 7}$$
3. C.exists and equals 4
4. D.exists and equals 0