The value of 299792458 meters per second 186282 miles per second is the speed of light in a vacuum. Light in water 225000 kms. Light in vacuum air 300000 kms.
In medium X its speed is 2108ms and in medium Y the speed of light is 25 x 108 ms.
The speed of light in a vacuum is equal to 670600000 miles per hour. The speed of light in air is 3108 ms. The fastest medium in which light can travel is through no matter which is a vacuum. The value of 3313 ms which represents the speed at 0 C or 27315 K is based on theoretical and some measured values of the heat capacity ratio g as well as on the fact that at 1 atm real air is very well described by the ideal gas approximation.