Actually, the domain is the possible set of input values of a function that will make the function fit the specific criteria. In this case, the input value is m, where m is the number of miles that is travelled. The criteria is to travel at least 10 miles but not more than 30 miles, therefore the domain should be:
All real numbers from 10 to 30, inclusive
(should be real numbers not integer since any fractional number is included in the domain)
I cannot figure out why the choices are far from the answer.