叔叔用8根a分米长的钢丝和4根b分米长的钢丝焊成  一个长方体的宠物房框架，它的体积是多少立方分米？[ ]

A.4ab

B.ab²

C.a²b

A merchant paid $300 for a shipment of x identical calculators. The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more than the average (arithmetic mean) cost of the X calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment ？（）

A．24

B．25

C．26

D．28

E．30