$[$The following information applies to the questions displayed below.$]$

Data for Hermann Corporation are shown below:

Per Unit Percent of Sales

Selling price $ $80100\%$

Variable expenses $4455$

Contribution margin $ $3645\%$

Fixed expenses are $$76,000$ per month and the company is selling $2,500$ 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 $$4$ per unit and increase unit sales by $20\%.$

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