(15.6, 12.4, 8.9, 6.66) = (x1,y1,z1,t1)
(3.84, 5.16, 4.20, 0)=(x2,y2,z2,t2)

Distance between 2 points on 4D:
d = sqrt((x1-x2)^2+(y1-y2)2+(z1-z2)^2+(t1-t2)2)
d = sqrt((11.76^2+7.242+4.7^2+6.662))
d = sqt(257.1608) = 16.036