(a) (b) Explain why mutual exclusion on certain portions of code can be an important requirement in the design of embedded systems. Explain what methods can be used to achieve mutual exclusion. Figure 3 shows a set of three tasks of a real time system that are to be scheduled using a rate monotone scheduler. The figure shows the trigger period and the computation period of each task. Each task must complete its computation before the task's next trigger time. The execution times of tasks are variable, so the table shows the fastest, slowest and mean execution time for each task. Task Period 30 A B 80 Computation time (ms) Priority Utilisation Min Max Mean 5 10 6.1 6 18 11.3 8 20 14.3 Figure 3 LOCO 00 000 120 (c) Complete the table showing priority P and utilisation U for each process. Use your answer to deduce whether or not the set should be regarded as schedulable by the rate monotone scheduling algorithm. The following line of Arduino code is used to generate a signal on pin 3 of a microcontroller: analogWrite (3,160) (0) Explain briefly what this line of code does and why it is useful. (i) What will be the average value of the voltage at pin 3 if the microcontroller board is an Arduino Nano? (ii) What will be the average value of the voltage at pin 3 if the microcontroller board is a Feather Huzzah? A simple condition monitoring system is based around a microcontroller which draws the following typical currents: 50 nA in sleep mode 20 mA in active mode (d) The device is in active mode when taking and recording measurements and is in sleep mode the rest of the time. The system must operate for at least 15 weeks without battery change. The power supply is 4.5V delivered by three 1.5V AA batteries Each of the batteries has a capacity of 1000 mAh. What percentage of the time must the device be in sleep mode to fit within the available power budget