如果商品X对于商品Y的边际替代率MRSXY小于X和Y的价格之比PX/PYJIK )。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='31439' and id < 2520434 and id<>'2520434' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='31439' and id > 2520434 and id<>'2520434' order by id asc limit 5