用电量为:W=UI1t1+UI2t2+UI3t3=U(I1t1+I2t2+I3t3)=220V×(0.3A×10×60s+0.4A×600s+0.2A×2400s)=1.98×105J1KWh=3.6×106J故W= 1.98×105 3.6×106 KWh=5.5×10?2KWh故选B.