Eliminating rows with identical data

I have a spreadsheet with about 6,000 rows of data in three columns:

Column A: Deparnment name.
Column B: Name of the employee.
Column C: Total expense for training.

The spreadsheet lists employees in multiple rows. For example, if John Smith recieved training on three different occasions, there would be three separate rows for him. I am trying to find the total number of employees for each department without double counting the employees. Is there some sort of excel formula I could use to do this? An IF statement maybe?

I've already sorted by department and by name, but that's as far as I've got.

Thank you for the help.

Thank you, I appreciate it. That was very helpful.