用一电动机提升处于匀强磁场中的矩形线圈，已知线圈的匝数为N，长为L，宽为d，质量为m，电阻为R，磁场的磁感应强度大小为B．开始时线圈的上边缘与有界磁场的上边缘平齐，当电动机匀速转动时，通过跨过两定滑轮的细绳将线圈提离磁场．若电动机转轮的半径为r，转速为n，求此过程中（重力加速度为g）

（1）细绳对线圈的拉力为多大？

（2）流过线圈导线横截面的电荷量是多少？

（3）电动机对线圈做的功为多少？

The following data sufficiency problems consist of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether.

A hiker in a national forest stopped at a ranger station to add water to her canteen. How many ounces of water were in the canteen when she arrived at the ranger station ？（）
(1) The hiker added 24 ounces to the canteen at the ranger station.
(2) After the hiker added water to the canteen, the canteen was 75 percent full.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.