The train can accelerate at a rate of 10 ft/s^2. It starts from rest and accelerates to its maximum cruising speed of 120 mi/h. 120 mi/hr = 176 ft/sec.
The distance traveled by the train while it accelerates is s = 176^2/(2*10) = 1548.8 ft. This in terms of miles is 0.293. The train then travels at 120 mi/h for 15 minutes. The distance traveled is equal to 120/4 = 30 mi.
The total distance traveled by the train is 30.293 miles.