I have a homework in which I had to average grades. Here is a picture. I've done everything correctly except the las step which I can't seem to understand. Once you see the image you will understand. I have to substitute the value of the cells under "NOTA #" with the letter corresponding to the number in "NOTA #" under the cell titled "Def"

For example, if the number under "NOTA #" ranges from 100-90 I need to make a formula that makes the letter A under "Def"

A B C D E F
100 - 90 90 - 80 80 - 70 70 - 50 50 - 30 30 - 0
excel.jpg