how do i compute the companys activity variances for may?

Jake's Roof Repair has provided the following data concerning its costs: For example, wages and salaries should be $20,900 plus $15.00 per repair-hour. The company expected to work 2,500 repair-hours in May, but actubly worked 2,400 repair-hours. The company expects its sales to be $47,00 per repair-hour. Required: Compute the company's activily variances for May. (Indicate the effect of each variance by selecting "F" for favorable, "U" for unfovorable, and "None" for no effect (i.e., zero variance). Input all amounts as positive values.)