A mining company is considering replacing its existing ventilation system with a new energy$-$efficient system. The new system will cost US$$300,000$ and is expected to save $180,000$ kWh of electricity annually. The current cost of electricity is $$0\mathrm{.}90$ per kWh$.$ The system has a life of $10$ years, with zero salvage value at the end of its useful life. Maintenance costs are assumed to be equal to the existing system$$s costs, so there are no net changes in operational expenses. Assume a corporate tax rate of $40\%$ and a minimum after$-$tax hurdle rate of $10\%.$ The investment will be depreciated straight$-$line over $10$ years. Use Discounted Cash Flow Rate of Return $($DCFROR$)$ and Net Present Value $($NPV$)$ methods to determine whether the investment is financially sound.