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 $ $26,000$

Variable expenses $14,000$

Contribution margin $12,000$

Fixed expenses $7,800$

Operating income $ $4,200$

$7.$ If the variable cost per unit increases by $$0\mathrm{.}50,$ spending on advertising increases by $$1,000,$ and unit sales increase by $250$ units, what would be the operating income? $($Do not round intermediate calculations.$)$