解:
在建设期内，各年利息计算如下:
q1=A1xi= x300x12%=18 (万元)
q2=(P1 +A2)xi= (300+18+ x 600 ) x12%= 74.16 (万元)
q3= (P2+A3)xi= ( 300+ 18+ 600+ 74.16+ x400 ) x12%= 143.0592 (万元)
建设期贷款利息= ql + q2 + q3= 18+74.16+143.0592 = 235.2192 (万元)