If the spring was initially compressed a distance of A, what would be the distance between points B and C that would cause the block to come to a stop at point C instead of traveling on to point D

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?