How to make a mixed or whole number 7/3

Arandom high school question but a hard one

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?

What is the absolute value of the complex number -4- 2 v14 3.15 14 18