Adding or Sum of Variables. Possible?

I'm making a simulation type game in storyline which has branching to different paths based on 3 different choices.

I made a variable called "Money from Company A", and i want this to be updated based on a given choice.

So let's say for simplicity:

Choice 1 - 10$

Choice 2 - 5 $

Choice 3 - 1$

If we have 5 questions in total, the maximum score should be 50$, and the minimum 5$, with a bunch of other possibilties.

The problem i was encountering was when a user is on the screen, and selects choice 1 then changes their mind to choice 2, the triggers i have set still add the points up. So a user can get more than 10$ on a question if they keep switching between choice 1 and choice 2.

I overcame this by making the variable change only when the user clicks the "submit" button at the end, so they have left the slide, and cannot change their answer.

All good up until this point.

But I was wondering whether or not I could calculate the sum of different variables, if I decided to add another company into my scenario? So in the results slide, I could show a total of the money earned from the two companies.

is there a function that could do %Money from A% + %Money from B% ? Or Sum(Variable1, Variable2)? 

The only solution I have now, is to display the two variables in the results slide, and have the person add it up manually.

Deniz