$1.$ Data concerning Sa Corporation's single product appear below:

$$

$$

$$

Per unit

Percent of sales

Selling price

P

$150$

$100\%$

Variable expenses

$$

$60$

$40\%$

Contribution margin

P

$90$

$60\%$

$$

Fixed expenses are P$445,000$ per month. The company is currently selling $6,000$ units per month. The marketing manager would like to introduce sales commissions as an incentive for the sales staff. The marketing manager has proposed a commission of P$9$ per unit. In exchange, the sales staff would accept a decrease in their salaries of P$43,000$ per month. $($This is the company's savings for the entire sales staff.$)$ The marketing manager predicts that introducing this sales incentive would increase monthly sales by $100$ units. What should be the overall effect on the company's monthly net operating income of this change?

A$.$ decrease of P$88,900$

B$.$ decrease of P$2,900$

C$.$ increase of P$42,100$

D$.$ increase of P$537,100$