There are 3 columns, A, B and C. Each column has 10 rows each containing
numbers. I need to find the standard deviation of the product of the numbers
in each row.
Eg:

a b c product
2 5 4 40
3 6 5 90
4 7 6 168

We need to find STDEV of the product column.
I need this without calculating the product separately just in one formula
which would give the stdev of the product.