Answer:
The total selling expenses for the quarter will be $25,800
Explanation:
The computation of the total selling expenses for the quarter is shown below:
= Salaries + commission + Advertising
where, 
Salaries = Expected salaries × number of months in one quarter
              = $5,000 × $3
              = $15,000
Commission = (January sales +  February Sales + March Sales) × Commission percentage
= ($25,000 + $30,000 + $35,000) × 10%
= $9,000
And, the adverting equal to
= Expected advertising expenses × number of months in one quarter
= $600 × 3 months
= $1,800
Now put these values to the above formula
So, the value would be equal to
= $15,000 + $9,000 + $1,800
= $25,800