求翻译：乙方为甲方电脑维护实行先工作后支付的方式，甲方在此合同生效后并为其工作的第二个月的5日前支付乙方上个月的电脑维护费，若遇节假日顺延，之后支付以此类推。同时乙方需提供有效发票。是什么意思？

B is paid after the first implementation of the work for Party A computer maintenance, computer maintenance fees to pay Party B last month in the Party after the entry into force of this contract and its work two months on the 5th case of extended holidays After payment and so on. Party B must provi

Party B to party with a first computer maintenance work, and the way to pay after a party after the entry into force in this contract and its work for the first 2 months of pay for 5 days before the party B last month computer maintenance, if extended holidays, after payment and so on. While Party B

The second party implements the method after the party of the first part computer maintenance which works first pays, the party of the first part after this contract activation and for before its work second month-long 5th pays the second party previous month the computer maintenance expense, if mee

Party b for party a computer maintenance manner of implementation of work before pay customer, this contract and to work for a second month after the entry into force last month payment before 5th str computer maintenance, section in case of holidays extended, after payment and so on. While party b

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