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