Calculation Widget not suctioning correctly

I am having an issue on the Form "Jons Clone of Advantage Rental Plan"

When you preview the form and select an instrument, the total cost of the instrument should show up on the end of the second page

Flute Clarinet and Alto Sax function correctly.  However the other instruments either do not show the total cost field or they have an incorrect value in the field.  

If the field is not hidden, it works, however we can't have the total for every instrument on the last page.  

Thank you

Hi,

I have tested many of the instruments and I see seem to be getting correct amounts.

Could you please elaborate on how the calculation works as I might be missing parts of it that need to be included?

Looking forward to your reply.