Write the implementation (.cpp file) of the GasTank class of the previous exercise. The full specification of the class is: A data member named amount of type double. An data member named capacity of type double. A constructor that accepts a parameter of type double. The value of the parameter is used to initialize the value of capacity. The constructor also sets amount to zero. A function named addGas that accepts a parameter of type double. The value of the amount instance variable is increased by the value of the parameter. However, if the value of amount is increased beyond the value of capacity, amount is set to capacity. A function named useGas that accepts a parameter of type double. The value of the amount data member is decreased by the value of the parameter. However, if the value of amount is decreased below 0, amount is set to 0. A function named isEmpty that accepts no parameters and returns a boolean value. isEmpty returns true if the value of amount is less than 0.1, and false otherwise. A function named isFull that accepts no parameters and returns a boolean value.. isFull returns true if the value of amount is greater than capacity-0.1, and false otherwise. A function named getGasLevel that accepts no parameters. getGasLevel returns the value of the amount data member. A function named fillUp that accepts no parameters and returns a double. fillUp increases amount to capacity and returns the difference between the value of capacity and the original value of amount (that is, the amount of gas that is needed to fill the tank to capacity).