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

Table 5

Simulation of the unit operating costs.

	2013	2014	2015	2016	2017	2018	2019	2020	2021
Simulation 1	32	35.24	36.47	40.67	46.07	55.00	54.14	55.69	48.59
⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮
Simulation 500	32	31.17	35.17	37.91	37.66	36.27	37.15	34.34	36.08
pdf𝑖
𝜇𝑖	32	32.41	33.12	33.51	34.05	34.56	35.16	35.80	36.35
𝜎𝑖	0.0	3.16	4.55	5.70	6.60	7.49	8.45	9.42	10.00
TFN𝑖
𝑎1𝑖=𝜇𝑖−2𝜎𝑖	32	26.09	24.02	22.11	20.85	19.58	18.26	16.96	16.35
𝑎2𝑖=𝜇𝑖	32	32.41	33.12	33.51	34.05	34.56	35.16	35.80	36.35
𝑎3𝑖=𝜇𝑖+2𝜎𝑖	32	38.73	42.22	44.91	47.25	49.54	52.06	54.64	56.35
𝛼𝑖=𝛽𝑖	0.0	6.32	9.10	11.40	13.20	14.98	16.90	18.84	20.00
INT𝑖
𝐶^𝑙𝑖 ($/t)	32	30.30	30.08	29.71	29.65	29.56	29.52	29.52	29.68
𝐶^𝑢𝑖 ($/t)	32	34.52	36.16	37.32	38.45	39.56	42.09	42.08	43.01