债务资本成本=8%×(1-25%)=6%普通股资本成本=3%+1.2×(13%-3%)=15%长期借款所占比重=[(2500+2500)/2]/[(2500+2500)/2+(1200+1200)/2+(5000+5000)/2+(1700+900)/2]=25%优先股所占比重=[(1200+1200)/2]/[(2500+2500)/2+(1200+1200)/2+(5000+5000)/2+(1700+900)/2]=12%普通股及留存收益所占比重=[(5000+5000)/2+(1700+900)/2]/[(2500+2500)/2+(1200+1200)/2+(5000+5000)/2+(1700+900)/2]=63%加权平均资本成本=6%×25%+10%×12%+15%×63%=12.15%