The perimeter of an isosceles triangle is 18 cm.Its lateral side and the base are in the ratio 7 : 4. The area of the triangle is

A

8 $$\sqrt{5} cm^{2} $$

B

6 $$\sqrt{5} cm^{2} $$

C

4 $$\sqrt{5} cm^{2} $$

D

10 $$\sqrt{5} cm^{2} $$