I have the following table:

3 2 1 0 -1 -2
< 4.6 A A-B B D E F
4.6- 6.9 A-B B C D E F
9-11.5 B B-C C D D E
11.5-13.8 C C-D D D D D
13.8 C D D D D D

I want to find, for example, what letter corresponds to (5,-1). I expect a
letter "E" to be the answer, but I have no idea how to write the formula.

Help!!!