Final answer:
The online furniture store must sell a minimum of 20 chairs in order to meet the requirements.
Step-by-step explanation:
To determine the minimum number of chairs that the online furniture store must sell in order to meet the requirements, we need to consider the total cost of chairs and tables. Let's break it down:
Tables: If the store sold 10 tables for $400 each, the total cost of tables is 10 * 400 = $4000.
Minimum sales requirement: The store must sell a minimum of $6500 worth of chairs and tables. Since the cost of tables is already $4000, the remaining amount should come from the chairs. Therefore, the minimum amount of chairs to be sold is (6500 - 4000) / 150 = 20.
So, the online furniture store must sell a minimum of 20 chairs in order to meet the requirements.