write a program that will read a line of text that ends with a period, which serves as a sentinel value. display all the letters that occur in the text in alphabetical order along with the number of times the letter occurs in the text. treat uppercase and lowercase letters as being equal (convert everything to upper or lower using. you will have to define a method that takes a letter and converts it to a number value. you will find it helpful when doing this to remember that you can type cast chars to ints, but will have to adjust their value by subtracting (int)’a’ to make them line up with the indexes in your array.