$f(5)-f(2)=0 \Rightarrow f(5)= f(2)$; thus, $f(x)$ is a constant function. Then, $f(8) - f(2) = 0$. 
Let $f$ be a linear function for which $f(5)-f(2)=0$. What is $f(8)-f(2)$? (  Adapted From 2003 AMC 12B Problems, Question \#9) 
Options:
(a) $$4$$ 
(b) $$2$$ 
(c) $$1$$ 
(d) $$0$$ 
(e) $$-3$$ 