public void addOperator(String op) {
		if (op.equals("add")) {
			add.setBounds(20, 160, 40, 40);
			masterLayer.add(add, new Integer(1));
		} else if (op.equals("subtract")) {
			subtract.setBounds(80, 160, 40, 40);
			masterLayer.add(subtract, new Integer(1));
		} else if (op.equals("multiply")) {
			multiply.setBounds(140, 160, 40, 40);
			masterLayer.add(multiply, new Integer(1));
		} else if (op.equals("divide")) {
			divide.setBounds(200, 160, 40, 40);
			masterLayer.add(divide, new Integer(1));
		}
	}