If x, y and z are Integers and z is not 0, Find range of (x-y)/z

Dear GMATinsight,

With all due respect, my friend, there appears to be some problems with this question.
1) In the prompt, the relationship of the three inequalities below the text is not clear. On a GMAT Quant question, something would be explicitly said. For example, the three inequalities might be stated above the words, and then the words could say, "If x, y and z are Integers in the ranges give above and ..." In one way or another, the words have to make clear reference to the role of those three inequality statements.

2) I believe there's a missing negative sign in choice (C), because otherwise, the expression could only equal 6.

3) Most importantly, given that those three equalities at the beginning specify ranges for the variables, then I don't find the answer listed.
If we want the numerator, the value (x + y), to have the biggest absolute value, x and y need to have the same sign.
x + y = 10 + 4 = 14 if we add the highest positive values
x + y = (-11) + (-5) = -16 if we add the lowest negative values: this is better.
To make this positive, we need to divide by the smallest allowable negative number, which is -1.
Max value = ((-11) + (-5))/(-1) = +16
To make this a large negative value, we would divide by the smallest allowable positive number, which is +1.
Max value = ((-11) + (-5))/(+1) = -16
The range is from -16 to +16, an option not given.

Does all this make sense?
Mike