Ans: C
$\begin{array}{rcl}
a_1 & = & a_2 – 6 \\
a_2 – a_1 & = & 6 \\
\end{array}$
$\begin{array}{rcl}
a_1 & = & a_2 – 6 \\
a_2 – a_1 & = & 6 \\
\end{array}$
Therefore, the common difference is $6$, Hence, we have
$\begin{array}{rcl}
\dfrac{28}{2} [ 2a_1 + ( 28-1)6] & = & 1624 \\
2a_1 + 162 & = & 116 \\
2a_1 & = & -46 \\
a_1 & = & -23
\end{array}$
