R-2.2 Draw an expression tree that has four external nodes, storing the numbers 1, 5, 6, and 7 (with each number stored one per external node but not necessarily in this order), and has three internal nodes, each storing an operation from the set {+,-, *,/} of binary arithmetic operators, so that the value of the root is 21. The operators are assumed to return rational numbers (not integers), and an operator may be used more than once (but we only store one operator per internal node). R-2.8 Illustrate the performance of the selection-sort algorithm on the following input sequence: (22,15,36,44, 10,3,9,13,29,25). R-2.9 Illustrate the performance of the insertion-sort algorithm on the input sequence of the previous