The slope is undefined because of the formula y2-y1/ x2-x1
in this case in (5,4) the 5 is x1 and the 4 is y1. in (5,8) the five is x2 and the 8 is y2. Pug the number in for the formula and you will see that it is D. undefined.
Since it takes 48 minutes to walk 6 laps, you can divide 48 by 6 to get how long it takes for him to walk one lap. Mickey will take 8 minutes to walk 1 lap.