7. ( 5 points) The following function converts a prefix expression to an infix expression assuming the expression can only contain unsigned integer numbers and " + " and " - " operators. public static String convert(String prefix) | stack s - new AStack: String operandi, operand2, infixi int i= prefix. length -1 : while (i>=0) ( char nextc = prefix.charAt (i); if ( (nextc =="+") (nextc ==+1) operandl =spop(); operand 2=spop(); inf 1x=1(+ operand 1+ nextc + operand 2+"); s.push (infix); i--; I else if (Character. isDigit (nextc)) i int end = i; while (Character. isDigit (prefix.charAt (i)) im; infix = prefix.substring (i+1, end +1); s. push (infix); ? else i; 1 return s.pop (); 1 (a) (2.5 points) Rewrite only the lines of code that need to be changed so that the above function converts a prefix expression to a postfix expression. r (b) (2.5 points) Describe in words what changes are needed on the above given convert () function so that it also finds the value of the converted prefix expression