104+105折舊=($208,000-$28,000)X(5+4)/15=$108,000
106年折舊=$60,000($100,000-$10,000)X2/3
(208000-28000)*5+4/15=108000
208000-108000=100000
100000-10000=90000
90000*2/(1+2)=60000折舊
106/1/1帳面價值280,000-60,000-48,000=100,000
(100,000-10,000)*2/3=60,000