ΔPQR is an isosceles triangle and PQ = PR = 2a unit, QR = a unit. Draw PX $$\perp$$ QR, and find the length of PX.

A

$$\sqrt{5}a$$

B

$$\frac{\sqrt{5}a}{2}$$

C

$$\frac{\sqrt{10}a}{2}$$

D

$$\frac{\sqrt{15}a}{2}$$