Jenny likes to exercise. When she goes to the gym she lifts weights and then does her cardio workout. To monitor the cardio part of her workout, Jenny uses a heart rate monitor. The graph below shows Jenny’s heart rate while she was on the treadmill.

1. What was Jenny’s heart rate when she first got on the treadmill?

   Answer (a):

   At time $t = 0$ Jenny’s heart rate was $85$ beats per minute (bpm).

2. Jenny worked out on the treadmill for $25$ minutes. She likes to get her heart rate up to at least $140$ beats per minute. How long was she at this heart rate?

   Answer (b):

   Jenny’s heart rate reached $140$ bpm around $17\text{-}20$ minutes in to her run. Her heart was at least $140$ bpm for $5 \text{-}8$ minutes.

3. What does the area under the curve represent?

   Hint (c):

   Multiply the units on the axes.