2 THE ASSIGNMENT E F A 5 A 4 4 3 1 4 Wally and Eva are two university students chosen by their faculty to compete in a robotics com- petition that will be held in a month's time. They have come up with the following list of tasks necessary to build their robot, along with the time each task takes in days, the cost associated with each task, and the precedence relationship between certain tasks: Task A B C D Preceding Task B C E Duration (day) Cost (RM) 400 800 520 600 255 600 (a) Draw the arrow diagram for Wally and Eva, and solve the problem to determine the follow- ing The minimum number of days needed to completely build the robot. Which tasks are critical. The cost of building the robot. [4%)