A new machine costs $$320000,$ has a useful life of $12$ years, and can be sold for $$30000$ at the end of its useful life. It is expected that $$10000$ will be spent to dismantle and remove the machine at the end of its useful life. Compute the depreciation rate $,$ the book values for years $1$&$12$ for this machine using: A$.$ straight$-$line method $.$ B$.$ the sum$-$of$-$years'$-$digits method $.$