Since it does not include 0 in the inequality, nor does it include any numbers below 0, it must be

.
Ava took 5 minutes out of 60 in an hour to do half a mile
5×2=10
60/10=6mph
Damon took 3 minutes out of 60
3×2=6
60/6= 10mph
Reina took 4 minutes out of 60
4×2=8
60/8= 7.5mph
That would be the number of permutations of 3 from 10.
= 10P3 = 10! / 7! = 10*9*8 = 720