Evaluation of Underground Zinc Mine Investment Based on Fuzzy-Interval Grey System Theory and Geometric Brownian Motion

Table 6

Operating costs over production period 2017–2021.

	2017	2018	2019	2020	2021
𝐶year (mill’s USD)	[2.965, 3.845]	[2.956, 3.956]	[2.956, 4.029]	[2.952, 4.208]	[2.968, 4.301]