Gravity Mechanics Question; How to work this out?

A ball is initially at rest. It falls from a height of 4m to the ground. Find
a)The time ot takes to fall to the ground
b)its speed when it hits the ground

answers
a)0.904s
b)8.85ms

please explain how to work this out, my teacher keeps setting homework on things we haven't even done in class (and then she gets pissed when no one's done their homework??) so I'm so baffled please help?

thank you

So I have s, u and a and I need to find out v and t? right?
s=4m
u=0
v=?
a=9.8ms^2
t=?

s=ut + 0.5at^2 ( use to find t)

v^2 = u^2+ 2as ( use to find v)

i`d point out to your teacher to teach you how to do these things before she asks you!