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You can do this using the regular Radio Option button(found in Form Tools) to create all the products, then do calculation for them, and then theTotal Amount of the calculation can be passed on to the paypal Custom Amount Payment tool (only the Total Amount.. so it is only one)
Review this user guide also -How-to-pass-a-calculation-to-a-payment-field
Here is an example form you can check http://www.jotform.me/form/41486574533461
I have added calculation value to the property of Radio option like this
so that it can be calculated.