Use this information for Rusty Co$.$ to answer the question that follow.

Rusty Co$.$ sells two products, X and Y$.$ Last year, Rusty sold $5,000$ units of X and $35,000$ units of Y$.$ Related data are as follows:

Unit SellingUnit VariableUnit ContributionProductPriceCostMarginX$$110$$$70$$$40$Y$705020$

What was Rusty Co$.\text{'}$s sales mix last year?

a$.60\%$ X$,40\%$ Y

b$.30\%$ X$,70\%$ Y

c$.58\%$ X$,42\%$ Y

d$.12\mathrm{.}5\%$ X$,87\mathrm{.}5\%$ Y