Which items could best be used to represent the sun , the earth , and the moon in a model that shows the phases of the moon

John is working part-time in an office. He works 30 hours per week and earns $600 each week. He currently has $2,700 in a savings account. John needs to spend $3,780 on car repairs. He sets aside $492 a week for his usual expenses. After spending all of his savings on car repairs, John decides to set aside 5% of his weekly salary to replenish his savings account. How many weeks will it take to get back to $2,700?

The sun could be a flashlight 
The earth could an orange 
The moon could be a bouncy ball