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. A constructor that no parameters. The constructor initializes the data member amount to 0. 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. 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. A function named getGasLevel that accepts no parameters. getGasLevel returns the value of the amount data member.

1. write a statement that declares a string variable named city. the variable should be initialized so it references an object with the string “san francisco”. a) assume that stringlength is an int variable. write a statement that stores the length of the string referenced by the city variable (declared in question1) in stringlength. b) assume that onechar is a char variable. write a statement that stores the first char- acter in the string referenced by the city variable (declared in question1) in onechar. c) assume that uppercity is a string reference variable. write a statement that stores the uppercase equivalent of the string referenced by the city variable (declared in question 1) in uppercity. d) assume that lowercity is a string reference variable. write a statement that stores the lowercase equivalent of the string referenced by the city variable (declared in question 1) in lowercity.