a. Risk Premium on J & M common stock = Return on Market - Risk Free Rate
Risk Premium on J & M common stock = 11% - 6%
Risk Premium on J & M common stock = 5%
b. Required Return = Rf + Beta * (RM - RF)
= 6% + 1.2*5%
= 6% + 6%
= 12%
So the required rate of return is 12% which should be atleast provided by J & M common stock.
c. J & M cost of common stock equity is the same as b that equals to 12%.