# Step-by-step: Ward's method for calculating linkage

I'm trying to use Ward's method to calculate linkage for hierarchical agglomerative clustering with the data points below: $$a=(0,0)$$ $$b=(1,2)$$ $$c=(3,4)$$ $$d=(4,1)$$ $$e=(2,2)$$ According to some software, after joining b and e, the distance between a and {b,e} is 2.88, but I cannot see how this is derived? Furthermore, I have not been able to find any step-by-step demonstration of calculating linkage using Ward's method online, if this could be explained would be very appreciated :)