12.98%
普通股资金成本率为:s=1.5/[50x(1-8%)]+10%=13.26%;
优先股资金成本率为:s=12/(1-4%)=12.5%;
则该企业的加权平均资金成本率为:w=Σi*i(t=1.2.3...n)=500x13.26%/(500+300)+300x12.5%/(500+300)=12.98%.