**To find the optimum amount of labor, we use MPN = real wage rate **

**A.** 0.2( 200 - N ) = 10

40 - .2N = 10

-.2N = -30

Divide both sides by -.2

**N = 150 **

**B. **with wage at $20

0.2 ( 200 - N ) = 20

40 - .2N = 20

-.2N = -20

Now Divide both sides by -.2

**N = 100 **

**C.** 0.5(200 - N) = 10

100 - .5N = 10

-.5N = -90

Divide both sides by -.5

**N = 180**