A 27 pound meteorite struck a car, leaving a dent 27 cm deep in the trunk. If the meteorite struck the car with a speed of 520 m/s, what was the magnitude of its deceleration, assuming it to be constant?

I just cant figure out how this is done. To find the magnitude of deceleration i belive i would need to divide the 520 m/s by some other time in seconds yet...there is no other time in seconds. Also, I havent an idea what im supposed to do with the pounds and dent. Is there a way to find out seconds from those or something? Im really stuck here. If someone could just guide me along or give me a formula to figure it how to do this it would be greatly appreciated, as I just cannot find one!