If $$cot\theta=\frac{a}{b}$$ then find the value of $$\frac{cos\theta+sin\theta}{cos\theta-sin\theta}$$

A

$$\frac{a-b}{a+b}$$

B

$$\frac{a^{2}}{b^{2}}$$

C

$$\frac{b}{a}$$

D

$$\frac{a}{b}$$