The difference between contribution margin and income from operations is $\_\_\_\_\_\_\_\_.$net incomevariable costsfixed costsNone of these choices are correct$\mathrm{.}2.$ The relationship between a companys contribution margin and income from operations is measured by $\_\_\_\_\_.$contribution marginoperating leveragemargin of safetybreak$-$even point$3.$ The $\_\_\_\_\_\_\_\_\_\_$ is the relative distribution of sales among the products sold by a company.sales mixmixed costproduct mixNone of these choices are correct$\mathrm{.}4.$ The unit selling price of the overall enterprise product equals the $\_\_\_\_\_\_\_\_.$average selling price of the productsprice of the highest$-$selling product in the mixsum of the unit selling prices of each product multiplied by its sales mix percentageprice of the product having the lowest selling price