The following questions ask you to write parts of the requirements specification for a heating system of a house. The heating system consists of a furnace and a digital thermostat. The thermostat has a controller, which will communicate with the furnace. The thermostat has a key pad with 10 digits, an "on" button, and an "off button on it. The thermostat also has an LCD display that shows at anytime the two digits that are dialed in by the user with the key pad as the desired temperature, and a sensor that measures the house temperature. If the house temperature is two-degrees lower than the desired temperature, the controller will activate the furnace; if the house is two-degrees higher than the desired temperature, the controller will deactivate the furnace. A fault can occur in the furnace. The controller can be reset after the fault recovery, and the furnace can be restarted by the controller once the controller is reset by the user The input signals (events) to the heating system are: N: user dials a digit to set the desire temperature O: user turns on the system . F: user turns off the system R: user resets the controller The output signals (events) from the system are: . T: the LCD display shows, when user pushes the "on" button D: the LCD display shows "d d", when the two digits, "d", "d", are dialed . E: the LCD display shows "E E", when there is an error in the furnace