IF AND … unless???

[KLNY152]

Current formula;

=IF(AND(B17=“Yes”,B18>2.9,B19=“Yes”,OR(B21>19,((B20>24)*(B20<50))),B25>0),”Yes”,”No”)

In essence returning a yes/no response to test the suitability of a candidate based on information given. 
however they will be tested against two different pathways. If the longer pathway cannot be done (because time is too short (B18)) then they can do the short even if the above formula returned a ‘no’. 
so I need it to be if the above formula is true, return yes. If the above returns no, but B20>49 AND B18<6 then this formula should return yes. As they will then be suitable because they can do it in place of the longer pathway. 

not sure if this makes any sense. 

please help! 

[#2]

If I understood your text correctly, this formula should be of some help.
=IF(AND(B17="Yes", B18>2.9, B19="Yes", OR(B21>19, (B20>24)*(B20<50)), B25>0), "Yes", IF(AND(B20>49, B18<6), "Yes", "No"))

[#3]

@KLNY152 

Perhaps

=IF(
    B18 > 2.9 + N("Long part"),
    IF((B17 = "Yes") * (B19 = "Yes"), "Yes", "No"),
    IF(
        OR(
            B21 > 19,
            (B20 > 24) * (B20 < 50)
        ) * (B25 > 0), "Yes", "No")
)