A motorcyclist started riding at highway marker \(\mathrm{A},\) drove 120 miles
to highway marker \(\mathrm{B}\), and then, without pausing, continued to
highway marker \(C,\) where she stopped. The average speed of the motorcyclist,
over the course of the entire trip, was 45 miles per hour. If the ride from
marker \(A\) to marker \(B\) lasted 3 times as many hours as the rest of the ride,
and the distance from marker \(\mathrm{B}\) to marker \(\mathrm{C}\) was half of
the distance from marker \(\mathrm{A}\) to marker \(\mathrm{B},\) what was the
average speed, in miles per hour, of the motorcyclist while driving from
marker \(\mathrm{B}\) to marker \(\mathrm{C} ?\)
A 40
B 45
C 50
D 55
E 60