if 350 miles on 20 gallons of gasoline. how many gallons will be used ro travel 875 miles under the same conditions

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?