A tuning fork vibrating with a frequency of $512$ $\mathrm{Hz}$ is kept close to the open end of a tube filled with water. The water level in the tube is gradually lowered. When the water level is $17$ $\mathrm{cm}$ below the open end, maximum intensity of sound is heard. If the room temperature is $20^{°}$ $\mathrm{C}$, calculate :
$(a)$ speed of sound in air at room temperature
$(b)$ speed of sound in air at $0^{°}$ $\mathrm{C}$.
$(c)$ if the water in the tube is replaced with mercury, will there be any difference in your observations ?