Working with student's results, in finding grades, sum of points and Division of each

[maduhu]

I was asked to compile student's results and each student takes at least 7 subjects and at most 12. The task is to calculate grades,weighing grades and summing
up the weights of 7 best performed subjects.
I used a nested if-functions to assign grades to scores and also to weigh the grades, If cell C2 is the reference one, then
=IF(A2>80,"A",IF(A2>60,"B",IF(A2>40,"C",IF(A2>30,"D","F")))) THIS ASSIGN GRADES,
=IF(B2="A","1",IF(B2="B","2",IF(B2="C","3"IF(B2="D","4","5")))) THIS WEIGHS GRADES,
The problem comes on how to sum up the weights of the 7 best performed subjects. May you please help me?

[oeldere]

You get better help if you add an excel file, without confidentional information.

Please also add the desired (expected) result.