Please show work and explain for all 3 questions so I can learn. Thank You!!!!!

Campus Auto Service offers towing and jump-starting services during the school year. August's financial information for these services follows. 7. Compute the overall weighted-average contribution margin per service call. 8. Chapman has a new parking restriction and Campus Auto expects towing services to become 40 percent of its total service calls in September. Compute the total number of service calls it must have in the following month to breakeven. 9. Refer to the original information. Assume Campus Auto Services has a tax rate of 25%. Compute the number of towing service calls Campus Auto Services will have when it earns an after-tax net operating income of $10,200