ll. Traffic Light Problem Traffic light control system needs a high level of coordination and concurency. In this problem, you are trying to develop a Petri Netfor traffic light control system. (1) To warm up, we will exhibit a toy example of two traffic lights. They are not allowed to signal green at the same time, shown in Fig-2-1. Please design a Petri Net to characterize the workflow of the two traffic lights. Fig 2-1 Two traffic lights (2) In a real situation, we will consider a cross road with intersection. We have a traffic light with 4 signal lights in a cross road shown in Fig. 2-2. It has the following four signal lights: a red light signal (R), a yellow (Y), a right turn arrow on green (GR), a straight arrow on green (GS). Regularly, turn left is permitted in any situation, so we don't need the left arrow green signal (GL) We have the following three rules for the traffic intersection. R1. The GS can be lighted up in opposite direction, shown in Fig. 2-3(a). R2. GR and GS of one direction can be both lighted up, shown in Fig. 2-3(b). To maximize the throughput of traffic, GS should be lighted when GR is lighted