A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all future shipments to equal the corresponding ratio for shipments S1, S2, S3 and S4 combined, as shown in the table above. What is the expected number of defective chips in a shipment of 60000chips?
S1>2>5000
S2>5>12000 S3>6>18000 S4>4>16000 （第一列为比率代号，第二列为number of defective chips in the shipment，第三列为total number of chips in the shipment） A.14 B.20 C.22 D.24 E.25 | 
