First, we will get the "n", the number of half lives, it is the elapsed time over the half life. In the problem, the time is measured in days, so we have
6/2 = 3
to get the ending amount of radioactive sample, we have
32g x (1/2)³ = 4 grams of radioactive sample ⇒ the amount left after 6 days
A) because you are moving closer to the moon
