Summarizing totals in main rpt for arrays in sub rpt

This report is combined Lawson and EPIC information.

The sub report is by customer and summarizes the total charges for every department the customer (patient) uses.

I have 3 shared arrays in a sub report that is grouped by customer (group1) and department(group2).
Array 1 is the count of each department and amount value.
Array 2 is the value of each department code.
Array 3 is the value of each department’s total charges.
There is an additional shared maximum value for the count of the department code value and associated charge amount arrays.
All of the shared arrays and the total count are displayed successfully in the main report.

The task is to add each customer’s department charges to a report total for each department. The totals should display in the main report footer.

How do I process the information from the 3 arrays (Count, Department Code value and Department Charge total) and add it to a summary total for each department?

Thank you.