Struggling with Excel IF Function for Employee Bands? Let's Solve It Together

This is the first time I am posting a question regarding a spreadsheet formula error.

In the attached screenshot, grades are given for respective employees. I want to enter their band via an IF function under the band column.

(=IF(F2= A, "50", Grade B= "40", Grade C= "30", Grade D= "20"))

=IF(F2="A", 50, IF(F2="B", 40, IF(F2="C", 30, IF(F2="D", 20, 0))))

---