Davis Company expects the following results for the next accounting period :

Sales 180000$

Variable costs 108000$

Fixed cost 35000$

Expected production and sales in units 2500

The sales manager believes sales could be increased by 625 units of advertising expenditure were increased by 14000$. If advertising expenditures are increased and sales increas by 625 units, the effect on operating income will be a :

a. decrease of 4000$

b. decrease of 14000$

c. increase of 18000$

d.increase of 4000$

(for the first one is easy, the operating income is 37000 but I could not find the other operating income after the increasing of units, please help and explain)