How to stack select and checkbox values ​​in angular?

Question

css

Hello! There is a working example where two selects add up to the final amount. How can I make the checkbox select instead of the second select? Those. when clicking on each check (and each has its own price in the $scope.matting array), it is added to the total. The whole demo with selects so far is here codepen.io/aderus/pen/PzzPKv
UPD. I tried like this codepen.io/aderus/pen/PzzEKN
Now I have the following problem. Checkboxes are counted among themselves and calculate percentages of the sum of two checkboxes. But how to combine in this amount (before calculating the percentage) also the choice of the select?