Let $$\triangle ABC \sim \triangle PQR$$ and $$\frac{ar(\triangle ABC)}{ar(\triangle QPR)} = \frac{144}{49}$$. If AB = 12 cm, BC = 7 cm and AC = 9 cm, then PR(in cm) is equal to:

A

$$\frac{49}{12}$$

B

$$\frac{108}{7}$$

C

$$\frac{21}{4}$$

D

$$12$$