Show how the billing plan whose graph is in Figure 1A.2 would change if the fee to unlock a scooter were increased from

$2 to $3.

An increase in the fee to unlock a scooter from $2 to $3 would increase the vertical intercept of the billing plan by $1 but would leave its slope unchanged. An increase in the fee to unlock a scooter thus leads to a parallel upward shift in the billing plan by $1, as shown in Figure 1A.3. For any given number of minutes the new bill will be $1 higher than the old bill. Thus, a 10-minute ride cost $3 under the original plan (point A) but $4 under the new plan (point A′). A 15-minute ride cost $3.50 under the original plan (point C), but $4.50 under the new plan (point C′). And a 20- minute ride cost $4 under the original plan (point D), but $5 under the new plan (point D′).

B ($/ride) 5 4.50 4 3.50 3 2 A' D 0 10 15 20 T (minutes/ride) New scooter bill Original scooter bill