3.1 Write a function which converts and returns Kelvin degrees into Fahrenheit degrees. The function should use a single parameter for the Kelvin degrees. The mathematical formula is):

F = K x 9/5 459.67 where F: Fahrenheit and K: Kelvin.

3.2 Write a function that calculates and returns the final price of a product. The function should have two parameters: one for the initial price and another for the tax.

The mathematical formula to be used is:

Final Price = Initial Price x (1 + Tax)