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 r2
8cm= 2144.66 cm
2cm=33.51cm
2144.66-33.51= 2111.15cm^2
hope that helped
-DBZ