we have

where
c---------> is the total cost of going to the carnival
t---------> is the number of
tickets purchased
we know that
the domain of the function is the interval---------------> [0,∞)
Because the number of tickets can not be negative
The range of the function is the interval-------------> [10,∞)
Because the total cost can not be negative
using a graph tool
see the attached figure
The answer in the attached figure