数学废求助两道jj题

jojolynUID: 4096678

1. Three variables, x,y,z, in a scientific experiment are related by the equation z=(x^2)y. In the experiment, if the value of x decreases by 40% while the value of y increases by 50%, what is the percent decrease in the value of z?
这题答案是18%，但是我怎么算都是46%啊:mad难道不是（0.6x)^2*1.5y=0.54x^2y所以下降了46%嘛？

2. A rectangular garden has a diagonal that is 26 feet long. If one side of the garden is between 8 feet and 12 feet long, which of the following values could be the area, in square feet, of the garden? 多选
A. 195
B. 200
C. 240
D. 265
E. 280
F. 300
答案是BCD,但除了C其他我完全不知道是怎么算出来的，有没有大佬能指点一下QAQ