The answer depends on the units used for 28 and 70. Are they inches, feet, yards, miles, metres? Since you have not bothered to share that crucial bit of information, I cannot provide a more useful answer.
630 square feet.
70 x 10 = 700 square feet.
14 feet x 70 feet = 980 square feet.
840 square feet.
7 * 10 = 70 square feet.
70 square meters = ~753.5 (753.473729) square feet.
14 × 5 = 70 square feet.
630 square feet.
70 x 10 = 700 square feet.
70 square meters = 753.473 square feet.
14 feet x 70 feet = 980 square feet.
840 square feet.
The answer is 70 560 square feet.
70 square feet on the ceiling, and another 70 square feet on the floor. We don't know how many square feet on the walls unles we know the height of the ceiling.
70 square meters = 753.47 square feet
Total square feet: 21,000.0
70 x 24 = 1,680 square feet.