Find all fourth degree polynomial $ p(x)$ such that the following four conditions are satisfied: (i) $ p(x)=p(-x)$ for all $ x$, (ii) $ p(x)\ge0$ for all $ x$, (iii) $ p(0)=1$ (iv) $ p(x)$ has exactly two local minimum points $ x_1$ and $ x_2$ such that $ |x_1-x_2|=2$.