请问We only work the flat tariff of 36 hours per

我们每周只有三十六小时收统一关税
flat tariff是指对通关时某一服务采取统一的收费标准
见下面的英语解释
flat tariff
A flat fee,also referred to as a flat rate or a linear rate,refers to a pricing structure that charges a single fixed fee for a service,regardless of usage.Rarely,it may refer to a rate that does not vary with usage or time of use.Another term used is "flate",a hybrid of "flat" and "rate".