89 km diameter asteroid will make a crater about 10 km in diameter. Let the asteroid have a density of 3000 kg/m3 and impact the surface at 25 km/sec....

A 0.89 km diameter asteroid will make a crater about 10 km in diameter. Let the asteroid have a density of 3000 kg/m3 and impact the surface at 25 km/sec. Assuming a spherical asteroid, what is the kinetic energy (in joule) of the asteroid? Convert the answer to megatons of TNT, where 1 megaton is about 4 × 1015 joule. For comparison, the most energetic weapon in the human arsenal is about 100 megatons.