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Required information

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Data for Hermann Corporation are shown below:

Fixed expenses are $$82,000$ per month and the company is selling $3,500$ units per month.

Required:

$1-$a$.$ How much will net operating income increase $($decrease$)$ per month if the monthly advertising budget increases by $$8,700,$ the

monthly sales volume increases by $100$ units, and the total monthly sales increase by $$11,000?$

$1-b.$ Should the advertising budget be increased?