Olivet Devices sells two models of fitness devices. The budgeted price per unit for the wireless model is $$40$ and the budgeted price per unit for the wireless and cellular model is $$85.$ The master budget called for sales of $41,600$ wireless models and $10,400$ wireless and cellular models during the current year. Actual results showed sales of $32,000$ wireless models, with a price of $$37$ per unit, and $12,600$ wireless and cellular models, with a price of $$82$ per unit. The standard variable cost per unit is $$27$ for a wireless model and $$62$ 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.