Joshua wants to burn at least 400 calories per day, but no more than 600. He does this by walking and playing basketball. Assuming he burns 4 calories per minute walking, w, and 5 calories per minute spent playing basketball, b, the situation can be modeled using these inequalities: 4w + 5b ≥ 400

4w + 5b ≤ 600

Which are possible solutions for the number of minutes Joshua can participate in each activity? Check all that apply.

40 minutes walking, 40 minutes basketball
60 minutes walking, 20 minutes basketball
20 minutes walking, 60 minutes basketball
50 minutes walking, 50 minutes basketball
60 minutes walking, 80 minutes basketball
70 minutes walking, 60 minutes basketball

The answer is D, and F
I know this because I just took the test.