Posted by john help me with this question plz on .
A planet orbiting a star is occasionally hit by comets. Each comet has a mass of
4.8 × 10^6 kg of which 30% is rock and 70% is water ice. Each time a comet hits the planet 40% of the mass of the comet is vaporised and the rest is added to the planet, increasing the mass of the planet. If 6 comets hit the planet every 10 years, by how much will the mass of the planet have increased in 1 million years? How much of the additional mass will be in the form of rock, assuming that the rock and ice evaporate in the same proportions as exist in the original comet? You should give both answers to one significant figure and in scientific notation. Be sure to complete both answers before clicking on “Enter answer”.
1)Increase in mass of planet after 1 Ma = ??? kg
2)Additional mass of rock after 1 Ma =???? kg

science help plzzzzzzzzzzzzzzz? 
drwls,
Sorry, John isn't here.
This looks to be just a bookkeeping problem. In a million years, 600,000 comets will impact. Each has a mass of
4.8 × 10^6 kg and leaves 60% behind as new planet mass. Rock will be 30% of the added mass.