A mass spectrometer similar to the one in Figure $\mathrm{P} 24.67$ is designed to analyze biological samples. Molecules in the sample are singly ionized, then they enter a $0.80 \mathrm{T}$ uniform magnetic field at a speed of $2.3 \times 10^{5} \mathrm{m} / \mathrm{s} .$ If a molecule has a mass 85 times the mass of the proton, what will be the approximate distance between the points where the ion enters and exits the magnetic field?
A. $25 \mathrm{cm}$
B. $50 \mathrm{cm}$
C .75 \mathrm{cm}$
D. 100 cm