Suppose you earn £1200. You purchase only shirts, which are £10 each, with your income every month..

Suppose you earn £1200. You purchase only shirts, which are £10 each, with your income every month. (a) What is the purchasing power of your income ? (b) Now, suppose your income increases to £1500 a month but the price of shirts remains the same. Does the purchasing power of your income change ? (c) Suppose your income remains £1200 but the price of shirts increases to £12 each. Does the purchasing power of your income change ?