Energy consumption is measured in units of kilowatt hours (kWh). The more kWh a household use in a month, the higher the energy bill. A power company charges customers $0.12 per kWh for the first 500 kWh. After the first 500 kWh, the rate is $0.15 per kWh. Write a program to calculate energy charge. You must write and use the following two functions. (a) A main function: Ask the user to enter number of kWh used. Call the bill_calculator function and pass number of kWh used to it as an argument. (b) A bill_calculator function: This function has a parameter to receive number of kWh used. Calculate and display the energy charge.