最近要开始节约啦。从生活点滴做起。可是刚收到了nationalgrid的NATURAL GAS BILL，发现列的一大堆数据都不是很懂啊。有哪位高人指点一下啊。叩谢啦！

下面是几个数据：

present Reading: 612

Previous Reading: 542

Gas Used: 70 ccf (这个没什么问题）

Therm Factor: 1.026 (这是啥？）

TOTAL Consumption: 70*1.026=71.820

接下来的更不明白了

Deliver Charges           

                                                 Quantity used        cost per therm

   Customer Charge                                                                                  $9.00

   usage charge step1                  71.820 Therms   *   $0.3600                 $25.86

   Distribution Adjustment charge  71.820 Therms *     $-0.0025               $-0.18

   Energy Efficiency Surcharge      71.820 Therms *    $0.0107                 $0.77

        Total  Delivery Charges                                                                                $35.45                                                 

Gas Charges

    cost of gas                                71.820 Therms * $1.0844                     $77.88

        Total  Gas Charges                                                                                        $77.88

Other Charges

    Gross Earnings Tax                                                                                $3.50

         Total other Charges                                                                                       $3.50

Total  Current Charges                                                                                            $116.83