If the current yield for AAA rated corporate bonds is 6%, the current yield for AAA rated municipal bonds is 5.2%, the current yield for AA rated corporate bonds is 5.5%, the current yield for AA rated municipals is 4%, the current 10-year Treasury Bond yield is 3.7%, and the current US T-Bill rate is 1.3%, then what is the risk premium for AA rated corporate bonds?

A) 1.8%

B) 2.7%

C) 1.5%

D) 4.2%

E) 4.7%