Let $z = \frac { x y } { x + y }$

Multiple Choice

Let $z = \frac { x y } { x + y }$ . Then $\Delta z$ , the change of z from (-1, 2) to (-0.9, 1.9) , is

A) 1.04
B) 0.87
C) 0.63
D) 0.29
E) 0.15