Give a context-free grammar for each of the following languages over S={a,b}: a) {a bi | i, j20) b) {aibiak | i+j=k, k>=0} Show the parse tree (up to depth 4) of the following Java program: import java.util.Scanner; class Ex{ public static void main(String[] args) { Scanner keyboard - new Scanner(System.in); System.out.println("enter a number"); double x - keyboard.nextDouble(); System.out.println("x2+2x+1 -" + x*x+2*x+1)