Find the "Grade", "Failed", "Due" function

In "GRADE" column: if average is >54 & <59.99 = D, if average is >60 & <79.99 = C, if average is >80 + B But, if 'math', 'phy' & 'che' is <33 & 'Bio'<50 = F.

In "Failed" column: if 'math', 'phy' & 'che' is <33 & 'Bio'<50 = show the name of individual failed subject name i.e. Math/Math & phy.

Pl help me to find out the solution in MS Excel.