The trajectory of projectile, projected from the ground is given by \( y = x - \dfrac{x^2}{20} \). Where \( x \) and \( y \) are measured meter. The maximum height attained by the projectile will be:
\( 5 \, \text{m} \)
\( 10\sqrt{2} \, \text{m} \)
\( 200 \, \text{m} \)
\( 10 \, \text{m} \)