#TODO ===== BEGIN SOLUTION HERE =====

    dirDOTnorm = np.dot(ray.viewDirection, self.normal);

    if (dirDOTnorm != 0): # If it is not parallel.

    	t = np.dot((np.array([0.,0.,0.]) - ray.eyePoint), self.normal) / dirDOTnorm;

    	if (t > EPS_DISTANCE): # If the t is positive.

			isect.t = t;
			isect.p = ray.eyePoint + t * ray.viewDirection;
			isect.n = self.normal;

			if (self.material2 == None): # If not checkboard.

				isect.material = self.material;

			else: # If checkboard.

				xz = np.ceil(ray.eyePoint + t * ray.viewDirection[0]) + np.ceil(ray.eyePoint + t * ray.viewDirection[2]);

				if (xz % 2 == 0): # If even.

					isect.material = self.material;

				else : # Odd.

					isect.material = self.material2;

    # ===== END SOLUTION HERE =====