Advanced Lookup and Average Nest Function

I have two columns of Data. One column is a how much sleep I got, which varies. The to other column is how i ranked my day on a scale of 1 -5. Then i have a column that lists 1-5 and next to it i want the averages of the hours i slept that I ranked according to rankings.

So if my sleep went
16,9,20,4,2
And my ranking column went
1,3,5,2,4

how can i create a formula that would be like find all the rankings for 3, look across the column in the sleep column and average that to the other ranking 3s?

thanks