Task: Question Answering
Input (English): Problem: the rate of spin of a certain gyroscope doubled every 15 seconds from the moment a particular stopwatch started. if after a minute and a half the gyroscope reached a speed of 400 meters per second, what was the speed, in meters per second, when the stopwatch was started ?
Options: a. 25 / 2, b. 25 / 4, c. 25 / 8, d. 25 / 16, e. 25 / 32
Output (English): b