January $1,$ Year $1,$ Ballard company purchased a machine for $$30,000.$ On January $1,$ Year $2,$ the company spent $$8,000$ to improve its quality. The machine had a $$3,600$ salvage value and a $6-$year life, which areunchanged. Ballard uses the straight$-$line method. What is the book value of the machine on December $31,$ Year $4?$