Manero Company included the following information in its annual report:

$2019$

$2018$

$2017$

Sales

$

$187,400$

$

$172,500$

$

$155,500$

Cost of goods sold

$115,000$

$102,500$

$100,000$

Operating expenses

$50,000$

$50,000$

$45,000$

Operating income

$22,400$

$20,000$

$10,500$

In comparison to year $2017,$ the effect of sales growth on operating income of $2018$ was $($ignore taxes$)$: