(15 pts) Use the branch and bound method to solve the following minimization problem. Use LINGO to solve all sub-problems, and use tree diagram to show all branch and bound solution process. Make notes for all nodes that are fathomed, and indicate the reasons for which they are fathomed. min s.t. wwwww z=50x1+100x2 7x1 + 2x2 >= 28 2x1 + 12x2 >= 24 x1, x2>=0 and integer.