I used to be good at phyics, but

[aviodont]

You got to think, when does y max occur.

When Vy=0, Y is at its highest.

So,...

 

[xxChrisxx]

so you know the

initial velocity
final velocity
acceleration

you can use
v^2=u^2+2as to find the max height (remember to +5ft)

v=u+at to find time