stmt - assignment subr call assignment - id := expr subr call - id ( arg list ) expr - primary expr tail expr tail - op expr + epsilon primary - id + subr call - (expr ) op - + | - | * |/ arg list - expr args tail args tail -, arg list - epsilon (a) construct a tree for the parse string foo(a, b) (b) Give a canonical (right-most) derivation of the same string