The file named Buslist.xlsx gives the amount of time between bus arrivals (in minutes) at 45th Street

Question:

The file named Buslist.xlsx gives the amount of time between bus arrivals (in minutes) at 45th Street and Park Avenue in New York City. Write a formula that, for any arrival time after the first bus, gives the amount of time you have to wait for a bus. For example, if you arrive 12.4 minutes from now and buses arrive 5 minutes and 21 minutes from now, you will wait 21 – 12.4 = 8.6 minutes for a bus.