For the following data, what is the ratio of the resistivities of resistor A to resistor B?

__Resistor A:__R (k-Ohms) = 2, radius (mm) = 1, L (cm) = 3

__Resistor B:__

R (k-Ohms) = 4, radius (mm) = 2, L (cm) = 6

A. 4:1

B. 2:1

C. 1:2

D. 1:4

The answer is D, but using the equation for resistance, R=(rho*L)/A, I keep getting a 2:1 ratio, or answer choice B. Any idea what I'm doing wrong?