Totals using a formula are incorrect

Hello colleagues,

Please consider this table: 

Column A is the number of underlying values in the row.

Column B is the numnber of distinct underlying values in the row.

Column C is the product of A and B (i.e. A * B).

If you do A * B across each row, you see the products are calculated correctly, including for the total row.

However if you sum each column, you'll see that A and B foot properly (totals equal the sum of the values above), but the A*B column does not sum.  This is because of rows 2 and 3, which have more rows than they have distinct rows.  Because the totals row is multiplying the sums of the individual columns A and B, the values of 21 in the second and third rows is being multiplied against the values of 5 and 271 in the first and fourth rows, creating a grand totals row that calculates across, but where the grand total for the A*B column does not equal the sum of the values.

Put another way, more simply, the grand total for A*B should be 73508.  I want the totals to sum down, even though it means the grand totals math will not work across.

I've been wracking my brain on how to accomplish this.