Floating rate mortgages became popular during the 1980s because _____. (a) high interest rates made it difficult for borrowers to qualify for fixed rate loans (b) floating rate loans were the only type of mortgage loans available for bundling (c) borrowers acquiesced to the assumption of interest rate risk (d) GNMA and FNMA issued guidance letters concerning buyers concessions on fixed-rate loans (e) floating rate loans were conceptually easier to underwrite than fixed rate loans for a portfolio lender (f) all of the above