Let \( 3, a, b, c \) be in A.P. and \( 3, a - 1, b + 1, c + 9 \) be in G.P. Then, the arithmetic mean of \( a, b \) and \( c \) is:
\( 13 \)
\( 11 \)
\( -4 \)
\( -1 \)