Olivet Devices sells two models of fitness devices. The budgeted price per unit for the wireless model is $$57$ and the budgeted price per unit for the wireless and cellular model is $$102.$ The master budget called for sales of $55,200$ wireless models and $13,800$ wireless and cellular models during the current year. Actual results showed sales of $40,500$ wireless models, with a price of $$54$ per unit, and $17,700$ wireless and cellular models, with a price of $$99$ per unit. The standard variable cost per unit is $$44$ for a wireless model and $$79$ for a wireless and cellular model.

Required:

a$.$ Compute the sales activity variance for these data.

b$.$ Break down the sales activity variance into mix and quantity parts