Discuss the surface mine planning and optimisation techniques that have been applied in junior opencast coal mining companies and analyse their effectiveness in terms of improving company performance. Your report should include a set of recommendations that you would make to your company, including any value$-$adding recommendations for more effective mine planning and optimisation of the company's surface mining operation$($s$).$ Also highlight the challenges and$/$or unresolved problems that still remain in the planning and optimisation of the surface mining operation$($s$)$ in your company, explaining why this is so$.$