[SOLVED} array of discount multiply to array of amount

hello friends i need a formula to solve this thing. i know how to do it in vba but i have to use a formula from my workbook.

well i have a around 50000 rows of discount and amount what i need is to get the result by multiplying the discount to amount.

discount column is in a percentage format.

discount is from column a and amount is in column b

=sum(a1:a50000)*sum(b1:b50000) wont work

sorry if my english is so bad but i attached a sample file to get what i mean.
hope you guys could help me. thanks.