Answer: D
A good way to approach this question is to take the log2, i.e. find the number of bits required to represent the number.
We use our rule that 1000 ≅ 10 bits.
Assume that a student has $8,000 and Bill Gates has $50,000,000,000. Representing student wealth requires 13 bits: 10 bits for 1,000 and 3 bits for 8 (23 = 8). Representing Bill Gates' wealth requires 36 bits: 3 * 10 bits for 1,000,000,000 and 6 bits for 50 (26 = 64).
Thus, in terms of log2, a student has a bit more than 1/3 of what Bill Gates has.
It is also easy to do this problem by counting digits in decimal: $8,000 is 4 digits, while $50,000,000,000 is 11 digits. 4 is a bit more than 1/3 of 11.
The lesson: log grows very slowly.