When cell phones were first introduced, bandwidth was limited, which led to economically interesting pricing structures. One by Spring offered 4,000 free minutes for $39.99 a month. The fine print revealed a catch. Only 350 of those minutes were anytime minutes; the remaining were restricted to evening and weekend usage. If you went over your allotted time, you were charged 35 cents per minute for any additional minutes.

• What was your marginal cost? Graph it.
• What would your average variable cost curve for peak time usage have looked like?
• If you did not keep track of your usage, how would you figure your marginal cost?
• Why did firms offer such confusing plans
• Were firms that charged this way in favor of or against portability of phone numbers?
• Why are these offers no longer prevalent?