[Plugin: Caldera Forms] How to multiply and other questions?

I am a happy user of caldera forms but I can’t seem to find a way to multiply.

For example a user selects an option from the drop down menu and a price appears, for example $10. Then the user wants to tick an add-on option and I want to multiply the result by 1.3 to end up with $13.

Another question is rounding the results. If I multiply $10 by 1.3 and then by 1.4 I end up with $18.2 but would like to have $18. This option would be great but is probably unavailable. But I don’t think that there is not such a thing as multiply. I simply can’t find it.

Many thanks