Calculating from a dropdown menu

I've created a form with a drop down menu, amongst other numeric fields.

The last field is my total...but I'm having issues getting the calculation to work correctly.

In the drop down i have 5 choices listed. Under binding on that drop down, I've given each item it's own value. so the first option is 1, next is 2, etc.

So in my calculation, i wanted to run an if statement. If option 1 from the drop down is chosen, then multiply x * .5. if option 2 is chosen, then multiply x * .75, etc.

This is what I have so far:

if (HasValue(buildingtype1)) then
$.rawValue = Concat(250*.50)
else
if (HasValue(buildingtype2)) then
$.rawValue = Concat(250*lots*.50)
else
if (HasValue(buildingtype3)) then
$.rawValue = Concat(500)
else
if (HasValue(buildingtype4)) then
$.rawValue = Concat(1000)
else
if (HasValue(buildingtype1)) then
$.rawValue = Concat(20000)
else
$.rawValue = ""
endif

Of course I get an error when i switch from design view to PDF view to test it....

I'm also wanting to add other things in that total field, not just this drop down box.

any suggestions?