For Fatma's utility function u(f,c) = f^0.4 * c^(-0.6), write the expression for the Marginal Rate of Substitution (MRS). Is her MRS diminishing?

a) MRS = 0.4 * f^(-0.6) * c^(-0.6); Yes
b) MRS = 0.4 * f^(-0.6) * c^(-0.6); No
c) MRS = 0.6 * f^(-0.4) * c^(-0.4); Yes
d) MRS = 0.6 * f^(-0.4) * c^(-0.4); No