Two arrows are shot vertically upward. The second arrow is shot after the first one, but while the first is still on its way up. the initial speeds are such that both arrows reach their maximum heights at the same instant, although these heights are different. Suppose the that initial speed of the first arrow is 21 m/s and that the second arrow is fired 0.306122448979592 seconds after the first. Determine the initial speed of the second arrow.