3. Bob travels horizontally to the right with a speed of 215 m/s. However, Bob cannot see very well, so he sends a sound wave with wavelength 0.0686 m in all directions to help him probe his surroundings. a) There is a wall to Bob's right and a wall to Bob's left: 215 m/s Bob Both walls reflect sound waves back to Bob. What frequency will Bob hear and what is the time interval between very loud sounds?b) For this part, suppose there are no walls. However, Bob's friend Alice is located to Bob's left: - 215 m/s Alice Bob Bob's sound wave reflects off of Alice and returns to him. Bob observes the reflected wave to have a frequency of 2090 Hz. Determine Alice's speed and the direction in which she moves (left or right)