Finding amplitude and period from SHM acceleration and displacement

[kandyfloss]

Homework Statement

Please find the question in the attachment,i've attached it because it includes a graph

Homework Equations

a=-(omega)^2.x
T=2.pie/omega
Vmax=omega.A

The Attempt at a Solution

for part b i used the first equation a=-(omega)^2.x to find omega and then substituted the value of omega in the second equation mentioned above.
a=-(omega)^2.x
omega=*sqrt*a/x
omega = 1.5/10
omega=0.39
and thus T=1.6 m/s
Please tell me if I'm right so far?
for part c
i can use the third eq but i can't figure out how to find the amplitude?

 

[kandyfloss]

i think this question should be in introductory physics section..
apologies!
Mods please move this :)