Final answer:
The function rule representing the total cost of BMX racing is C(r) = 40 + 15r, which entails a $40 fixed fee for a racing license plus $15 per race.
Step-by-step explanation:
The function rule that represents your total cost C at a bicycle motocross (BMX) track, where you pay a fixed cost for a racing license and a variable cost per race, can be determined by combining these costs. In this case, you pay a fixed fee of $40 for the racing license and an additional $15 for each race, r. The total cost, C, can be found by multiplying the number of races, r, by $15 and then adding the fixed fee of $40.
The function rule that represents the total cost C for a racing license plus the cost per race is C(r) = 40 + 15r, option b. The $40 represents the fixed cost of the racing license, which does not depend on the number of races. The $15r represents the variable cost per race, where r is the number of races.
Therefore, the function rule for the total cost C is:
C(r) = 40 + 15r
This means for each race you enter, your total cost increases by $15, on top of the initial $40 fee for the racing license.