Can anyone help me with this physics problem?

You toss a tennis ball straight upward. At the moment it leaves your hand it is at a height of 1.5 m above the ground, and it is moving at a speed of 8.4 m/s.

(a) How much time does it take for the tennis ball to reach its maximum height (in seconds)?
t = Vo/g = 8.4/9.8 = 0.857 sec


(b) What is the maximum height above the ground that the tennis ball reaches (in meters)?
H = ho+Δh = 1.5+Vo^2/2g = 1.5+8.4^2/19.6 = 5.10 m


(c) When the tennis ball is at a height of 2.6 m above the ground, what is its speed (in meters per second)?
V = √Vo^2-19.6*(2.6-1.5) = √8.4^2-19.6*1.1 = 7.00 m/sec

I think there is some missing information.

Mass of ball, for starters. If you imagine a heavier ball of the same size (eg: one injected with water) and texture (same, smoother - or not), it'll perform differently.

Surely mass or weight would be a factor in the formula.