Answer
See below.
Work Step by Step
The midpoint $M$ of the line segment from $P_1(x_1,y_1)$ to $P_2(x_2,y_2)$ is: $(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})$.
$M=(\frac{2007+2013}{2},\frac{345+466}{2})=(2010,405.5)$.
The result we get is $405.5$ billion which is really close to the reported amount.
