I need help figuring out arithmetic sequence problem.

A large asteroid crashed into a moon of a planet, causing several boulders from the moon to be propelled into space toward the planet. Astronomers were able to measure the speed of one of the projectiles. The distance (in feet) that the projectile traveled each second, starting with the rst second, was given by the arithmetic sequence 24, 36, 48, 60, . . .. Find the total distance that the projectile traveled in seven seconds. C) 324feet C) 396feet o 420 feet C) 168feet