8, 12, 16, .....96
a = 8, d = 4, l = 96, n = 20
\(S_{20} = \frac{n}{2}(2a + (n-1)d\)

\(S_{20} = \frac{20}{2}((2\times 8) + (20-1)\times 4)\)

\(S_{20} = 10(16 + (19\times 4)) = 10 \times 92\)

=920