else if condition is not returning value to document.write()

I'm new to coding, so pardon me if my query isn't worth your time, but my code isn't resulting in the output I desire.

I'm trying to get a value calculated and placed on the page, depending on whether a user has input in the fields or not...

No value shows up on the page at all... Please advise...

Please pursue the image for the code and help me fix the issue