How to show totals for columns

I created a Sales Report in Opportunities where Main Group is Probability % field (90,80,50, and 25). The report groups all Opportunities by these percentages and I am able to sum each of these Probability groups based on the Opportunity Amount field. So I have four sub-totals.

Is there a way to sum the entire Opportunity Amount column? I currently have to manually total the four amounts to arrive at a total for the entire report.

Follow-up question, Is there a way to group the sales people (Assigned to field) within each of the above Probability % field?

Thank you in advance.