Answer: 315 square feet is needed for carpeting and It costs $2835.
Explanation:
Since we have given that
Length of room = 21 feet
Width of room = 15 feet
As we know the formula for "Area of room ":

Hence, 315 square feet is needed for carpeting.
Cost of per square foot of carpeting = $9
Total cost will be

Hence, it costs $2835.