Answer:
An increase in sale for 90 units, will increase the net income for 1$,170
Explanation:
We are not given with any information of additional cost or special price for this units, so we use the current values.
So we simply multiply the contribution per unit by the increase in sale.
Contribution Margin x Δ sales = Δ income
13 x 90 = 1,170
Each unit contributes with 13 additional income, there are 90 additional units
Total income added 1,170