The acceleration due to gravity at a place is g=9.61 ms. The speed with which a ball must be thrown vertically upward from the ground level so that it reached a maximum height of 50 m is

(a) 28 ms⁻¹
(b) 30 ms⁻¹
(c) 31 ms⁻¹
(d) 29 ms⁻¹