Answer:
40d > 600
Explanation:
In order to find the number of days the store needs to sell, you need to determine the number of shirts the store sells in a day, which is 40. If you multiply the number of shirts the store sells in a day (40) with the number of days its open (d), you get 40d. 40d must be greater than 600, since the store needs to sell more than 600 shirts.