You have rupees 200 to spend transport for 4 days. This works out to rupees 50 per day. Therefore, you on know that you need to take bus (one-way fare rupees 20) rather than an auto rickshaw (one-way fare rupees.50). On day you take bus to and fro and are able to stay within budget. On day 2, you are late and take an auto. Even if you take bus back home, you will be rupees 10 short or rupees in spite of saving rupees 10 the previous day. You will need to re-plan to adjust this deficit from the amount you have left. What amount do you have left for the remaining 2 days?​