Question

Yazmin decided to get some exercise by taking the stairs from the first to the fifth floor in her apartment building. The first time she went up the entire flight, she walked up some steps and ran up 16 steps. This took a total of 60 seconds.
The second time she went up the entire flight, she walked up some steps and ran up 28 steps. This took a total of 42 seconds. How long would Yazmin take if she walked up the entire flight of steps? (You may assume constant rates for walking and running.)

I'm not sure where to start since I have no total stairs.