A radioactive element's decay is described by the equation R = 50(0.5)ⁿ, where R is the amount after n half-lives. What equation represents the amount of radioactive material present in 50 grams after n half-lives?
a) R = 50(0.5)ⁿ
b) R = 50(2)ⁿ
c) R = 50n
d) R = 50/n