I need a step by step explanation to problem 14-23 in order to make me understand the solution:

14-23 Flexible Budgets and Operating-Income Variance Analysis: Spreadsheet Application

The following information is available for Brownstone Products Company for the month of July:

	Actual	Master Budget
Units	3,800	4,000
Sales Revenue	53,200	60,000
Variable manufacturing costs	19,000	16,000
Fixed manufacturing costs	16,000	15,000
Variable selling and administrative expenses	7,700	8,000
Fixed selling and administrative expenses	10,000	9,000

Set up a spreadsheet to compute the July sales volume variance and the flexible-budget variance for the month in terms of both contribution margin and operating income.

Discuss implications of these variances on strategic cost management of Brownstone.

Configure your spreadsheet so that it will allow the firm to prepare pro forma budgets for activities within its relevant range of operations. Use your spreadsheet to prepare a flexible budget for each of the following two output levels:

3,750 units

4,150 units