JOHN runs at different speeds as part of his training program, the graph shows his heart rate at different times during his workout on which interval is the target heart rate strictly increasing than strictly decreasing. So, when they say strictly that means it is only increasing and then only decreasing within that interval, there is nothing else. Let's take a look at these intervals here, the first part we are increasing, then we stay level, then we decrease so not not a single part in that interval is going to work for us. The second one we are increasing, then we decrease, then we increase then we stay the same. Okay, so only really just a part of that works for us. What about the last one, the last one increases, that stays the same didn't decrease as well.

We don't want that either because we plateau at that point. So this one will work. This won't work. And only this part of the interval actually works for us. So from 40 to 60 minutes Which is answered me