Hi i have a excel sheet of people with their average handling time like

ray 00:38:42
james 01:08:57
tommy 00:51:29
jin 00:33:38
tim 01:28:57


now i want to grade them like
people with <= 00:45:00 grade 5
people with <=00:50:00 grade 4
people with <=00:55:00 grade 3
people with <=1:00:00 grade 2
people with =1:01:00 grade 1

how do i use the formula in this