Sorting Results With IF Statement

Here is a sample of my data in the column starting at I2:

1600 (I2)
57000 (I3)
256000 (I4)
5700000 (I5)

I want to sort results so that the adjacent column gives a ranking code of "A" , "B" , "C" or "F"

my requiremetns are:

iF I2 = less than 65,500 then "A"

IF I2 = 65001 - 250000 then "B"

If I2 = 250001 - 1,000,000 then "C"

If I2 > 1,000,000 then F

The folks at "A" are above average, "B" are average, "C" below aveage with significant concerns and "F" are Critical nonformance, immediate action required.

Of course I plan to copy the formula down the range.