SharePoint List Calculated Column Multiselect Point Addition

Lets say the choice column was multiselect, meaning you could select multiple options. How would I go about adding the points up on the second column? 

Below is my example and error I'm getting: 

(I have three selectable options and gave them all 2 points each for a total of 6 points. Lets say I were to select "Multiple Users" and "20 Users," that should equal up to 4 points. If I selected all three options from the drop down menu, it would be 6 points. So I have two columns related to this. First column is "Collaboration" and second column is "CollaborationCalculated" which is a Calculated Field. When I add this formula below in the "CollaborationCalculated" column it works until I make the "Collaboration" column to Allow multiple selections. I get the below error which says: "unsupportedFieldTypeError." Is there an IF statement with addition involved to make this work?) 

=IF([Collaboration]="Multiple Users",2,

IF([Collaboration]="20 Users",2,

IF([Collaboration]="10 Users",2,"")))