Data for Hermann Corporation are shown below:

Per Unit Percent of Sales

Selling price $ $85100\%$

Variable expenses $5160$

Contribution margin $ $3440\%$

Fixed expenses are $$77,000$ per month and the company is selling $2,600$ units per month.

$2-$a$.$ Refer to the original data. How much will net operating income increase $($decrease$)$ per month if the company uses higher$-$quality components that increase the variable expense by $$5$ per unit and increase unit sales by $20\%.$

$2-$b$.$ Should the higher$-$quality components be used?