Write a menu-driven program that completes each task using a recursive function. A shell program is available from your teacher.

• Write a function called letters that takes a lower case letter as its argument and displays the sequence of letters from 'a' to the given letter.
  For example:
  Letters('a'); displays a and Letters('d'); displays abcd

• Write a function called twos that takes a single integer as its argument and returns the number of factors of 2 in the number. (Hint: odd numbers have no factors of 2, numbers that are twice an odd number have one, numbers that are four times an odd have two, and so on.)
  For example:
  System.out.print(twos(-12)); returns 2

• Write a Boolean function called powerof3 that takes a single positive integer argument and returns true iff the integer is a perfect power of 3 such as 1, 3, 9, 27, 81, ...
  For example:
  

  if (powerof3(81))
  	System.out.println("81 is a power of 3."); 
  else
  	System.out.println("81 is not a power of 3.";

  displays 81 is a power of 3

• Write a function called reverse that takes a single long integer argument and returns the result of reversing its digits. For partial credit, write a void function that just displays the number in reverse.
  For example:
  System.out.print(reverse(-12)); returns -21
System.out.print(reverse(1234567)); returns 7654321

• Write a function called base5 that takes a single nonnegative integer argument and displays its base five equivalent.
  For example:
  base5(136); displays 1021
base5(5); displays 10

• Bonus! Write a function called printWithCommas that takes a single nonnegative long integer argument and displays it with commas inserted properly.
  For example:
  printWithCommas(12045670); displays 12,045,670
printWithCommas(1); displays 1
  

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