1. Department of Industrial Engineering, Stellenbosch University, 145 Banghoek Rd., Stellenbosch 7600, South Africa
2. ESB Business School, Reutlingen University, Alteburgstr. 150, 72762 Reutlingen, Germany
3. Department of Mechanical and Mechatronic Engineering, Stellenbosch University, 145 Banghoek Rd., Stellenbosch 7600, South Africa