On July $1,20$X$1,$ Reeves Theatre purchased new sound equipment for $$60,000.$ The equipment has an estimated usefule life of five years and a salvage value of $$20,000.$ The sum$-$of$-$the$-$years'$-$digit method is used to calculate depreciation. What is the book value of the equipment at June $30,20$x$3?$