If $$\left(2 \frac{a}{m} + \frac{b}{n} \right) = 2$$ and $$\left(\frac{a}{m} - \frac{b}{n} \right)= 4$$, find the values of 'a' and 'b' respectively.

A

2m, -2n

B

-2n, 2m

C

2m, 2n

D

-2m, 2n