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

Table 7

Discounted cash flow over production period 2017–2021.

	2017	2018	2019	2020	2021
𝑅year (mill’s USD)	[2.279, 7.466]	[1.974, 7.360]	[1.672, 7.269]	[1.374, 7.192]	[1.079, 7.131]
𝐶year (mill’s USD)	[2.965, 3.845]	[2.956, 3.956]	[2.956, 4.029]	[2.952, 4.208]	[2.968, 4.301]
𝑅year−𝐶year	[−1.566, 4.501]	[−1.982, 4.404]	[−2.357, 4.313]	[−2.834, 4.240]	[−3.222, 4.163]
Discount factor	[1.07, 1.10]	[1.14, 1.21]	[1.23, 1.33]	[1.31, 1.46]	[1.40, 1.61]
Present value	[−1.423, 4.206]	[−1.638, 3.863]	[−1.772, 3.506]	[−1.941, 3.236]	[−2.001, 2.973]