[经] pay-off method for capital investments

zī běn tóu zī huí shōu nián shù fǎ ㄗ ㄅㄣˇ ㄊㄡˊ ㄗ ㄏㄨㄟˊ ㄕㄡ ㄋㄧㄢˊ ㄕㄨˋ ㄈㄚˇ