Depending on the amount of scarves you sell, you will multiply that amount to $20 since that is the unit rate. For example, if you sold 5 then you would multiply; 20 * 5 = $100.
0.00065/5 will give you 0.00013 which can be written as 1.3x10^-4 and multiply that by 10^-2, you will add the exponents -4+-2 and get -6 as your new exponent, ending with 1.3x10^-6