Execute the following functions:
a) Function celsius returns the Celsius equivalent of the Fahrenheit temperature utilizing the calculation C= 5.0/9.0 * (F-32);
b) Function fahrenheit returns the Fahrenheit equivalent of the Celsius temperature utilizing the calculation F = 9.0/5.0 * C + 32;
c) Use these functions in order to write a script which allows the user in order to enter either a Fahrenheit temperature and show the Celsius equivalent or enter a Celsius temperature and display the Fahrenheit equivalent. Your HTML document must consists of two buttons, one for initiating the conversion from Fahrenheit to the Celsius and one for initiating the conversion from Celsius to the Fahrenheit.