What can the weighted average contribution margin ratio be used for?   Multiple Choice To solve for a measure, at any level of sales volume, of the sensitivity of operating profit to changes in volume. Breakeven and profit planning for sales volume expressed in dollars (Y) rather than units (Q). To calculate an average per-unit contribution margin based on an assumed sales mix. To figure out the relative proportion in which a company’s products (or services) are sold. To determine the extent of fixed costs in an organization’s cost structure.

Tennair Corporation manufactures cooling system components. The company has gathered the following information about two of its customers: Evans Equipment and Rogers Refrigeration. Evans Equipment Sales revenue Rogers Refrigeration $ 160,000 61,000 Cost of goods sold General selling costs $ 229,000 102,000 37,000 23,800 28,500 General administrative costs 17,850 Cost-driver data used by the firm and traceable to Evans and Rogers are: Customer Activity Sales activity Order taking Special handling Special shipping Customer Activity Sales activity Order taking Special handling Special shipping Cost Driver Sales visits Sales orders Units handled Shipments Evans Equipment 12 visits 31 orders 460 units. 33 shipments Pool Rate $ 970 278 44 460 Rogers Refrigeration 9 visits 36 orders 410 units 44 shipments Required: A. Perform a customer profitability analysis for Tennair. Compute the gross margin and operating income on transactions related to Evans Equipment and Rogers Refrigeration.

Please explain this statement thoroughly.  "To estimate what the profit will be at various levels of activity, multiply the number of units to be sold above or below the break-even point by the unit contribution margin."

Change in operating income = change in sales dollars x contribution margin What is the equation for the "change in sales dollars"?