Help with my "if and" formulae and boolean values

Hi Guys,

Got an issue with a numbers spreadsheet that I'm making. It's a salary breakdown form for my workforce and I want to automate it as much as I can. One of the ways I am trying to do this is in regards to automatically calculating whether an employee has perfect attendance for a month in question.

How I do this is create a column for days taken off and a second column for whether perfect attendance is relevant to the employee in question as not all employees have this.

Now, if the first column has 0 (as in 0 days taken off) and the second column has "yes" (as in yes he is viable for perfect attendance) then he will automatically get an additional 200. My current formula is as such:

(if (and perfect attendance = yes, days taken off = 0),+200,+0)

The problem is that if the days taken off field is blank this also counts as 0 so the extra salary is given. Is there any way for the formula to only recognise the digit 0 as being true and not the blank field as well?

Thanks so much.