Let $$O$$ be the origin, $$\overrightarrow{OP} = \vec{a}$$ and $$\overrightarrow{OQ} = \vec{b}$$.If $$R$$ is the point on $$\overrightarrow{OP}$$ such that $$\overrightarrow{OP} = 5\overrightarrow{OR}$$,and  $$M$$ is the point such that $$\overrightarrow{OQ} = 5\overrightarrow{RM}$$. Then $$\overrightarrow{PM}$$ is equal to :

A

$$\frac{1}{5}(\vec{a} - 4\vec{b})$$

B

$$\frac{1}{5}(\vec{b} - 4\vec{a})$$

C

$$\frac{1}{5}(-\vec{a} + 4\vec{b})$$

D

$$\frac{1}{5}(-\vec{b} + 4\vec{a})$$