This is a simulated version of a simple model of a coffee vending machine. In this model, the machine accepts 2 types of coins - a 5 rupees coin and a 10 rupees coin. A coffee costs 10 rupees. If the machine gets 10 rupees, it dispenses coffee. If it gets more than 10 rupees( 5 rupee coin put first and then a 10 rupee one), it dispenses coffee and gives change.