Platelet cells in blood play an essential role in the formation of clots and exist in normal human blood at the level of about 200 000 per cubic millimeter. In order to illustrate that diffusion alone is not responsible for transporting platelets, consider the following situation. The diffusion constant for platelets in blood is approximately 5 × 10⁻¹⁰ m²/s. About how long would it take a platelet to diffuse from the center of an artery (diameter 8.0 mm) to a clot forming on one wall of the artery?