Oslo Company prepared the following contribution format income statement based on a sales volume of $1,000$ units $($the relevant range of production is $500$ units to $1,500$ units$)$:

Sales $ $90,000$

Variable expenses $49,500$

Contribution margin $40,500$

Fixed expenses $33,210$

Net operating income $ $7,290$

Foundational $5-12($Algo$)$

Assume the amounts of the companys total variable expenses and total fixed expenses were reversed. In other words, assume the total variable expenses are $$33,210$ and the total fixed expenses are $$49,500.$ Using the degree of operating leverage, what is the estimated percent increase in net operating income of a $5\%$ increase in unit sales?