$($a$)$ The BVM Corp., a construction company, purchased a used hybrid electric pickup truck for $$30,000$ and used MACRS depreciation in the income tax return. During the time the company had the truck, they estimated that it saved $$9500$ a year. At the end of $4$ years, BVM sold the truck for $$9000.$ The combined federal and state income tax rate for BVM is $28\%.$ Compute the after$-$tax rate of return for the truck. $($b$)$ Hybrid electric vehicles $($HEVs$),$ such as the truck purchased by BVM Corp., are recognized for their fuel efficiency and earth$-$ friendliness. However, no major technology is without negative environmental impacts. Summarize the key environmental issues, such as greenhouse emissions in use, life$-$cycle impacts of battery sources $($such as lithium$-$ion and nickel metal hydride$),$ vehicle production impacts, and other life$-$cycle impacts.