1960 AHSME Problem 17

The formula N=8 \times 10^{8} \times x^{-3/2} gives, for a certain group, the number of individuals whose income exceeds x dollars. The lowest income, in dollars, of the wealthiest 800 individuals is at least:

\textbf{(A)}\ 10^4\qquad \textbf{(B)}\ 10^6\qquad \textbf{(C)}\ 10^8\qquad \textbf{(D)}\ 10^{12} \qquad \textbf{(E)}\ 10^{16}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.