Try one of these

Excel 2007 or higher
=IF(OR(B20<13,SUM(COUNTIFS($A$2:$A$19,{"1a";"2a";"3a"},$B$2:$B$19,"N"))),"Fail","Pass")

Earlier versions
=IF(OR(B20<13,SUMPRODUCT(--ISNUMBER(MATCH($A$2:$A$19,{"1a";"2a";"3a"},0)),--($B$2:$B$19="N"))),"Fail","Pass")