7. A grammar for infix expressions follows: 1 Start E $ 2 E T plus E 3 | T 4 T T times F 5 IF 6 F (E) 7 | num (a) Show the leftmost derivation of the following string. num plus num times num plus num $ (b) Show the rightmost derivation of the following string. num times num plus num times num $ (c) Describe how this grammar structures expressions, in terms of the precedence and left- or right- associativity of operators