I have no clue where to even start. For A, B or C. any formulas are much appreciated.

My instructor just types stuff into microsoft excel really fast and doesnt explain what he is doing so i REALLY need help.

Rock Solid Bank and Trust (RSB\&T) offers only checking accounts. Customers can write checks and use a network of automated teller machines. RSB\&T earns revenue by investing the money deposited; currently, it averages 5.80 percent annually on its investments of those deposits. To compete with larger banks, RSB\&T pays depositors 0.50 percent on all deposits. A recent study classified the bank's annual operating costs into four activities. Data on two representative customers follow. Required: a. Compute RSB\&T's operating profits. b. Compute the profit from Customer A and Customer B, assuming that customer costs are based only on deposits. Interest costs =0.50 percent of deposits; operating costs are 4 percent (=$24,000,000/$600,000,000) of deposits. c. Compute the profit from Customer A and Customer B, assuming that customer costs are computed using the information in the activity-based costing analysis