Colorado Business Tools manufactures calculators. Costs incurred in making $9,100$ calculators in February included $$29,500$ of fixed manufacturing overhead. The total absorption cost per calculator was $$11\mathrm{.}30.$

Required:

Calculate the variable cost per calculator.

The ending inventory of calculators was $820$ units higher at the end of the month than at the beginning of the month. By how much and in what direction $($higher or lower$)$ would operating income for the month of February be different under variable costing than under absorption costing?

Express the calculator cost in a cost formula.