What is the difference between a nominal value and a real value?a. A nominal value is measured in monetary units adjusted for inflation, unlike a real value. b. A nominal value is measured in market rates while a real value is measured in terms of exchange rates. c. A nominal value is measured in units of constant purchasing power while a real value is measured in units of current purchasing power. d. A nominal value is measured in current market prices while a real value is measured in base year prices.