40 Points Overlapping Dot Plots

A researcher uses a program that plots two sets of data on the same number line in order to highlight overlapping data points, such as in the example below.

from "Overlapping Dot Plots"

Having plotted data set A, she will now plot data set B (shaped as shown when plotted correctly). If the mean of data set B is 6, how many data points will overlap when both sets are plotted together?

(The first picture is the background info, the second picture is for the question)