since it is hollow, you need to take the whole volume minus the air inside

heres a diagram ish

| | | |

| | inside | |<------- outside glass

| | | |

3cm 2cm 3cm

<<---------8cm-------------->>

so, thats the ball

now we find volume

v=4/3 pi r^{2}

^{8cm= 2144.66 cm}

^{2cm=33.51cm}

^{2144.66-33.51= 2111.15cm^2}

hope that helped

-DBZ