a)
For example, for the 400 calories burned he covered 40 minutes, that can be seen from the graph.
The number of minutes per calorie burnt:
= 40 minutes / 400 calories
= 0.1 minute / calorie
So David ran 0.1 minute for each calorie burned.
b)
Slope of the graph formed:
Let us take any two points on the graph are:
The x axis has minutes and the y axis is for the calories.
(0 mins , 0 calories) and (40 minutes and 400 calories)
Slope = (Change in Calories) / (Change in minutes)
Slope = (400 - 0) calories / (40 - 0 ) minutes
= 400 calories / 40 minutes
Slope = 10 calories/minute
I hope this helps.