The real rate of interest is

a. the rate of interest determined by the returns earned on investments in productive assets (capital investment) in the economy

b. the nominal rate of interest determined by individuals' time preference for consumption

c. determined during periods of high inflation

d. always observable because most industrial economies operate with some degree of inflation, and periods of zero inflation are rare.

e. All of the above are correct

f. Only A, B, and C are correct