The original price of a dress is $39.99. Julie buys the dress when it is on sale for 10% off its original price. Two weeks later, Mindy buys the same
dress when it is now on sale for 20% off its original price.
How much more money did Julie spend than Mindy on the dress?
$ [blank]
Enter your answer as a number. If it is a decimal, round it to the nearest whole number, like this: 42