Three people travel home in the same taxi. They decide to divide the taxi bill in proportion to the readings on the taximeter. When the first person exits the taxi, the reading is [[$ 5 $]] QAR. When the next person exits the taxi, the reading is [[$ 10 $]] QAR. When the last person exits the taxi, the reading is [[$ 12 $]] QAR. How much does it cost to be the first to leave for a taxi?



Answer: The first person that leaves has to pay QAR.