在城市邮政设施需求量预测中，在预测通信总量（万元）和年邮政收入（万元），通常采用（）等预测方法。

A.发展态势延伸法

B.单因子相关系数法

C.双因子相关系数法

D.发展态势收缩法

E.综合因子相关系数法

The total cost for Company X to produce a batch of tools is $10,000 plus $3 per tool. Each tool sells for $8. The gross profit earned from producing and selling these tools is the total income from sales minus the total production cost. If a batch of 20,000 tools is produced and sold, then Company X’s gross profit per tool is （）

A．$3.00

B．$3.75

C．$4.50

D．$5.00

E．$5.50