Write a program that can serve as a simple calculator. This calculator keeps track of a single number (of type double) that is called result and that starts out as 0.0. Each cycle allows the user to repeatedly add, subtract, multiply, or divide by a second number. The result of one of these operations becomes the new value of result. The calculation ends when the user enters the letter r for Ac€A?resultAc€?? (either in uppercase or lowercase). The user is allowed to do another calculation from the beginning as often as he or she wants. Use the scanf for input.

The input format is shown in the following sample dialog. If the user enters any operator symbol other than +, ?, *, or /, then display message Ac€A?UnknownOperator is thrown Ac€A? and the user is asked to reenter that line of input..

            Calculator is on.

            result = 0.0

            +5

            result + 5.0 = 5.0

            result = 5.0

            *2.2

            result * 2.2 = 11.0

            result = 11.0

            % 10

            % is an unknown operation

            Reenter, your last line:

            * 0.1

            result * 0.1 = 1.1

            result = 1.1

            r

            Final result = 1.1

            Again?  (y/n)

          y

          result = 0.0

          +10

          result + 10.0 =10.0

          result = 10.0   

          /2

          result / 2.0 = 5.0

          result = 5.0

          r

          Final result = 5.0

          Again? (y/n)

          n

          End of Program