My teacher doesn't teach me can you guys help me

Me. i can't figure out this question. give an explanation too. .

I’m confused on how to work the pie charts

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?