If x and y are positive numbers and z = xy^2, a 40 percent increase in x and a 20 percent decrease in y would result in which of the following changes in z?  Choose the correct choice from the following answers.
A) decrease of 6.5% B) decrease of 10.4% C) increase of 4.3% D) increase of 12.8% E) increase of 16.7%
After the changes, z = 1.4x*(0.8y)^2 = (1.4*0.64)xy^2 = 0.896*z   The answer is decrease of 10.4%.
<result>B</result>
If x and y are positive numbers and z = xy^2, a 40 percent increase in x and a 20 percent decrease in y would result in which of the following changes in z?