A stone is projected vertically upward. While rising, its speed is 14m s−1 at a height of 20m above the point of projection. Neglecting air resistance and taking g=9.8m s−2, calculate the initial speed of projection.
(a) 20.0m s−1
(b) 14.0m s−1
(c) 24.3m s−1
(d) 34.3m s−1