Answer is B.

Would like to know why that is the answer.

10. What is the formula for the rate is paid to the inverse floater class in the following scenario: Floater and inverse floater securities are created with 80M allocated to the floater class and 20M allocated to the inverse floater class. The mortgages in the pool have a WAC of 6%. The floater class is paid LIBOR+30bp A. X=LIBOR B. X=0.288-4LIBOR C. X-LIBOR-30bp D. X=0.057-l(45)"LIBOR] E. X-0.285"(1/5)"LIBORI