During the first 48 to 72 hours of fluid resuscitation therapy after a major burn injury, the intravenous infusion rate will be adjusted by evaluating which of the following observation

A. Daily body weight.
B. Hourly urine output.
C. Hourly urine specific gravity.
D. Hourly body temperatur

如图所示，质量m=10kg的木块在与竖直方向成37⁰的力F的作用下沿竖直墙壁匀速上滑，已知木块与墙壁间的动摩擦因数μ＝0.5，sin37⁰=0.6，cos37⁰=0.8，重力加速度g取10m/s²。求：

（1）      F的大小？

（2）      若木块在F的作用下匀速下滑，则F又为多大？