请教一道数学题，没读懂

A farmer has a field that measures 1000 ft wide by 2000 ft long. There is an untillable strip 20 ft wide on the inside edge of the field, and a 30 ft wide untillable strip bisects the field into two squares (approximate). Approximately what percentage of the field is tillable?

A) 98%

B) 93%

C) 91%

D) 90%

E) 88%

A cylinder holds 10 liters of water. All of the water is poured into a cube, 50 cm on a side. What is the depth of the water (1 liter equals 1000 cubic cm of water)?

A) 4cm

B) 10cm

C) 40cm

D) 60cm

E) 100cm

内层四边有20尺的田埂（姑且这样称呼吧）中间有一个30尺的田埂把天地分开

通过查字典，strip ＝带状；untillable＝不可耕种的；

（我画了个图，其实就是求中间可以耕的面积和总面积的比例）

d:\1.gif

然后你就算呗。