Olivet Devices sells two models of fitness devices. The budgeted price per unit for the wireless model is $$43$ and the budgeted price per unit for the wireless and cellular model is $$88.$ The master budget called for sales of $44,000$ wireless models and $11,000$ wireless and cellular models during the current year. Actual results showed sales of $33,500$ wireless models, with a price of $$40$ per unit, and $13,500$ wireless and cellular models, with a price of $$85$ per unit. The standard variable cost per unit is $$30$ for a wireless model and $$65$ 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.