Mid Is Bad Velocity

$A, B, C$ and $D$ are four collinear points such that $AB = BC = CD$ . If the average velocities between $A$ and $B$ , $C$ and $D$ are $12 \text{ m/s}$ and $20 \text{ m/s}$ respectively, then what is the average velocity between $B$ and $C$ , if the body moves with uniform acceleration throughout?