26000
1.X5折舊費用=(108,000-3,000)*(5/(1+2+3+4+5))*(1/2)=17,500
2.X6折舊費用=(108,000-3,000)*((5/(1+2+3+4+5))*(1/2)+(4/15)*1/2)=31,500
X6/12/31設備BV=108,000-17,500-31,500=59,000
3.X7折舊費用=(59,000+19,000)*(5/(1+2+3+4+5))=26,000