How do i get dropdown selection to add up in formula field?

How do i get dropdown selection to add up in formula field?

When selecting options from both dropdowns

Dropbox1             
Option1=115.00
Option2= 89.00
Option3= 74.00

Dropbox2
Option1= 130.00
Option2= 74.00
Option3= 12.50

how do I added up and displayed in the formula field?

Thank you