[经] variation of estimated cost of materials

yuán liào gū jì chéng běn chā é ㄩㄢˊ ㄌㄧㄠˋ ㄍㄨ ㄐㄧˋ ㄔㄥˊ ㄅㄣˇ ㄔㄚ ㄜˊ