Your daily workout plan involves a total of 40 minutes of running and swimming. you burn 20 calories per minute running and 10 calories per minute swimming. let r be the number of minutes you run. how many calories will you burn in your 40 minuet workout if you run for 20 minutes

Calories burned per minute running  is 20 calories per minute
Calories burned per minute swimming is 10 calories per minute
the calories burned per minute while running can be modeled be:
C(r)=20r
where r is the number of minutes run. Thus the total number of calories burned after running for 20 min will be:
C(r)=20×20=400 calories