In July 2011, Beijing opened 114 telephone registration service. Aunt Guo went to work for 23 days in August this year, receiving an average of 144 calls per day, which is 18 fewer calls per day than when she was working in August last year. If Aunt Guo went to work for 21 days in August last year, how many calls did she answer this month?
2011年7月，北京开通114电话挂号业务．郭阿姨在今年8月份共上班23天，平均每天接电话144个，比去年8月份上班期间平均每天少接了18个电话．如果郭阿姨去年8月份上班21天，那么这个月她接了多少个电话？
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