A ball is thrown at the ground from the top of a tall building. The speed of the ball in meters per second is
v(t) = 9.8t + v0,
where t denotes the number of seconds since the ball has been thrown and v0 is the initial speed of the ball (also in meters per second). If the ball travels 25 meters during the first 2 seconds after it is thrown, what was the initial speed of the ball?