EXACT Functionality with non-sequential coloumns

My code for calculating alphabetic grade is below,it is working properly for sequential coloumns

How to change this code ,when non-sequential columns are considered ,means how EXACT(R5:V5) will be change if R5,T5,V5 are only considered for EXACT function means not all successive columns are considered .

=IFERROR(IF(SUMPRODUCT(--EXACT($R5:$V5,"a"))>0,"a",IF(((COUNTIF(R5:V5,"A")*3)+(COUNTIF(R5:V5,"B")*2)+(COUNTIF(R5:V5,"C")*1))/COUNTA(R5:V5)>=2.1,"A",IF(((COUNTIF(R5:V5,"A")*3)+(COUNTIF(R5:V5,"B")*2)+(COUNTIF(R5:V5,"C")*1))/COUNTA(R5:V5)>=1.1,"B",IF(((COUNTIF(R5:V5,"A")*3)+(COUNTIF(R5:V5,"B")*2)+(COUNTIF(R5:V5,"C")*1))/COUNTA(R5:V5)>=0.1,"C","")))),"")


Earlier I posted but I didnt get answer for that ,pls provide some solution for this issue