If $$a = 45^\circ$$ and $$b = 15^\circ$$, what is the value of $$\frac{\cos(a-b) - \cos(a+b)}{\cos(a-b) + \cos(a+b)}$$?

A

$$2 - 2\sqrt{2}$$

B

$$3 - \sqrt{6}$$

C

$$3 - \sqrt{2}$$

D

$$2 - \sqrt{3}$$