By using the following formula we can calculate the volume;
C₁V₁ = C₂V₂
C₁ = concentration of starting solution = 0.098m
V₁ = volume of starting solution that is needed for titration = 20.01ml
C₂ = Desired concentration of final solution = ?
V₂ = desired volume of final solution = 0.215g = 0.215ml
Now putting the values in the formula;
0.098 x 20.01 = C₂ x 0.215
C₂ = 0.215 / 1.96098 = 0.109m = 0.11m
Thus, the answer is 0.11m.