(i) Some part of the maintenance of the equipment must necessarily take place pari passu with the act of using it (e.g. oiling the machine). The expense of this (apart from outside purchases) is included in the factor cost.

(i) 设备维护的某些部分必须与使用它的行为同时进行（例如给机器上油）。这方面的费用（外部采购除外）包含在要素成本中。