41.2x8.1+11x1.25+53.7x1.9
=41.2x8.1+1.1x12.5+41.2x1.9+12.5×1.9
=41.2×（8.1+1.9）+（1.1+1.9）×12.5
=41.2×10+3×12.5
=412+37.5
=449.5