No, that answer is wrong it should be C, because 10*5^3 would be 5,000 then by multiplying it by 0.006 it would equal to 30. And 3*10^4 is equal to 30,000 not 30 but C. Which is 3*10^1 is like saying 3*10 once which is 30. So your answer should be C. Hope I explained this well for you Goodluck :)