would appreciate it if someone can help me with the question I have no idea how to get the answer...

If we graph Mary's indifference curves with avocados on the horizontal axis and grapefruits on the vertical axis,
then whenever she has more grapefruits than avocados, the slope of her indifference curve is -2. Whenever
she has more avocados than grapefruits, the slope is -1/2. Mary would be indifferent between a bundle with 14
avocados and 20 grapefruits and another bundle that has 22 avocados and
A) 11 grapefruits
B ) 15 grapefruits
C) 13 grapefruits
D) 16 grapefruits
E) 4 grapefruits

This post was edited by shadex151 on Feb 9 2014 01:10am

For initial condition:
14 avocados and 20 grapefruits, more grapefruits so slope is 2 grapefruits to 1 avocado. Exchange until equal.
14, 20
15, 18
16, 16

Now we have 16 of each, and need to exchange until we have 22 avocados, but since we will have more avocados than grapefruits the exchange rate is backwards - 2 avocados for 1 grapefruit

16, 16
18, 15
20, 14
22, 13

Answer is C, 13 grapefruits