Your income is $100 a month. You sign up for a telephone plan that costs $10 a month plus 10 cents per call.

18.Once you've signed up for the phone plan, draw your budget constraint between phone calls and "all other goods", with "all other goods" measured in dollars.

19.Now suppose the phone company offers an alternative plan that costs $20 a month plus 5 cents per phone call. You like this plan better so you switch; after switching, you make fewer calls per month. Illustrate this situation with indifference curves.

20.True or False: Given the information in question 19, phone calls must be a Giffen good for you.

21.True or False: Given the information in question 19, phone calls must be an inferior good for you.