Hard Question? How to solve it?

The speed of sound is 343 m/s. It will take 50/343 = 0.147 seconds for the drummer's sound to reach the conductor. So the violinist should wait 0.147 seconds. The speed of light is 3*10^8 m/s, and takes only 6*10^-6 seconds to reach the drummer from the conductor. Small enough to ignore.