A machine with a $4-$year estimated useful life and an estimated $15\%$ residual value was acquired on January $1.$ Would depreciation expense using the sum$-$of$-$the$-$years$-$digits method be higher or lower than depreciation expense using the double$-$declining balance method in the first and second years? First Year Second Year a$.$ Higher Higher b$.$ Higher Lower c$.$ Lower Higher d$.$ Lower Lower