Let $$\triangle ABC \sim \triangle RPQ$$ and $$\frac{ar(\triangle ABC)}{ar(\triangle PQR)} = \frac{1}{4}$$. If $$PQ = 4$$ cm, $$QR = 6$$ cm and $$PR = 7$$ cm, then $$AC$$ is equal to.

A

2 cm

B

4 cm

C

3 cm

D

3.5 cm