Q$.2.$ Suppose that the general demand function for good X is

QD $=500-5$PX $+0\mathrm{.}5$M $+10$PY $-2$PZ

where

QD $=$ quantity demanded of good X per month

PX $=$ price of good X

M $=$ Average consumer income, in thousands

PY $=$ price of good Y

PZ $=$ price of good Zc$)$ Based on the demand curve above, Are goods X and Y substitute or complements? What is the

relationship between good X and Good Z$?$ Explain