Find all values $x=$a where the function is discontinuous, determine if the discontinuity is removable or non$-$removable. For each value of $x,$ give the limit of the function as $x$ approaches $a.$ Be sure to note when the limit doesn't exist and explain how you know.

a$)f(x)=\frac{2-x}{x^2(x5)}$

b$)f(x)=\frac{x^3-9x}{x^{2}3x}$

c$)p(x)=-3x^{4}2x^{3}5x-8$