P, Q ,R and S are the points on line joining the points P(a,x) and T (b, y) such that PQ = QR=RS=ST, then $\left(\frac{{\displaystyle 5a+3b}}{{\displaystyle 8}},\frac{{\displaystyle 5x+3y}}{{\displaystyle 8}}\right)$ is the mid point of