13. Calculation of equivalent volumes of titrant in photometric and polarographic titration. Find the equivalence point on the next curve (mathematically and graphically).
V, ml 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
D 0.72 0.64 0.57 0.50 0.45 0.48 0.52 0.60 0.67 0.75