1. Extend the problem (exercise 2) of the last chapter (8) to repeat the operation until the word end is entered for one of the values. (Hint: use an infinite loop, and then do a last if either value is read.) 2. Rewrite the exercise from Chapter 4, Control Structures, summing numbers up to 999, using a loop that exits from the middle. (Hint: use a naked block with a redo at the end to get an infinite loop and a last in the middle based on a condition.)