Formula for adding two custom Dropdown lists

I have two custom dropdown list with money value:

1st Dropdown list
Name: [PF_SELECT1]
Values : Pro, Standard, Basic (one per line)
Default Values : empty
Fee Values : 50, 10, 5 (one per line)
Fee Field : Yes
Required: Yes

2nd Dropdown list
Name: [PF_SELECT2]
Values : Annual, Semi, Quarterly (one per line)
Default Values : empty
Fee Values : 100, 50, 25 (one per line)
Fee Field : Yes
Required: No

In my Payment Form, user is required to choose on 1st Dropdown list and has option to choose on 2nd Dropdown list.
If they choose one on each, the total should add up on the amount to be paid.

Appreciate your help in helping doing the formula on my form.

Thanks.

I left the calculation blank and it add up automatically. I guess this is solved.