A quarterly electricity bill shows the following charges:
For the first 50 kWh (kilowatt hours): 9.10c per kWh
For the next 150 kWh: 5.80c per kWh
Thereafter: 3.56c per kWh
a Write down a formula relating cost, $C, to n, the number of kWh of electricity used:
i for the first 50 kWh
ii for the next 150 kWh
iii for more than 200 kWh