A tuning fork with a frequency of 440 Hz is held just above the top of a uniform glass tube containing water. The glass tube can help excite the column of air above the water to form standing waves. The level of the column of air above water can be changed by a spigot at the bottom of the glass tube. As the water is drained out, the sound intensity of the fork is enhanced when the air column has a length 0f 0.6 m and again when the air column has a length of 1m. What is the speed of sound in air?