Required information

$[$The following information applies to the questions displayed below.$]$

Data for Hermann Corporation are shown below:

Fixed expenses are $$86,000$ per month and the company is selling $2,800$ units per month.

Required:

$1-$a$.$ How much will net operating income increase $($decrease$)$ per month if the monthly advertising budget increases by $$9,100,$ the

monthly sales volume increases by $100$ units, and the total monthly sales increase by $$13,000?$

$1-$b$.$ should the advertising budget be incrseaed