Modify the “mini calculator” from exercise 5 to accept (just) single-digit numbers written as either digits or spelled out.

Data from Exercise 5

Write a program that performs as a very simple calculator. Your calculator should be able to handle the four basic math operations — add, subtract, multiply, and divide — on two input values. Your program should prompt the user to enter three arguments: two double values and a character to represent an operation. If the entry arguments are 35.6, 24.1, and '+', the program output should be The sum of 35.6 and 24.1 is 59.7. In Chapter 6 we look at a much more sophisticated simple calculator.