please help with explanation

The following information is available for Brownstone Products Company for the month of July: Actual Master Budget 3,700 4,000 Units $54,100 $60,000 Sales revenue 10,400 16,000 Variable manufacturing costs 13,800 Fixed manufacturing costs 12,300 6,900 8,000 Variable selling and administrative expenses 9,900 8,400 Fixed selling and administrative expenses Required: 1. Compute the July sales volume variance and the flexible-budget variance for the month in terms of both contribution margin and operating income. (Indicate the effect of each variance by selecting "F" for favorable, "U" for unfavorable, and "None" for no effect (i.e., zero variance). Input all amounts as positive values. Flexible-Budget Sales Volume Variance Variance Contribution margin Operating income