If and excel formula for matching

Hi I am not sure how to write an excel formula to fulfill the below criteria

1. If Cell A1, B1 and C1 are the same | Show "Yes"
2. If Cell A1, B1 are the same but C1 is blank (vice-versa) | Show "Yes"
3. If Cell A1, B1 are the same but C1 is different (Vice-versa) | Show "Need to Update"
4. If Cell A1, B1 and C1 are all blank | Show ""

=IF(AND(A1="",B1="",C1=""),"",IF(AND(A1=B1,B1=C1),"Yes",IF(AND(A1=B1,C1=""),"Yes",IF(AND(A1=B1,B1<>C1),"Need to update","None of the above"))))