For this question, write a function to help a travel agent calculate the cost of a trip for a family. The trip

includes a flight and some number of nights in a hotel. The hotel sleeps at most $2$ people in each room.

Write a Python function that takes four parameters as input and RETURNS the total cost of the trip. The

four parameters should be the airfare per person in dollars, the room cost per night in dollars, the number

of travellers, and the number of nights.

Importantly, your function should do no console input and no console output. It must receive its input

through its parameters and send its output using a return value