please help me to find a and b ?

Method 1. To determine the concentration and the dissociation constant of the unknown acid solution (a) Calibrate the pH meter using the pH 4 and 7 buffer solutions B (b) Accurately titrate 25 cm of the unknown acid with standard sodium hydroxide solution 0.10 mol dm from a burette. In a table record the pH after the addition of each aliquot of sodium hydroxide (up to a total volume of 40 cm) in the box below. 8 NN ON Naph PH NOOH PH added cm3 addedcm 2.09 20 10.77 12.14 21 11.29 2 12.21 22 11.45 3 2.31 22.20 11, 52 4 22.40 11.55 5 2.47 2260 11. 58 2.59 2296 11.60 7 2.61 23.00 11.63 8 2.69 23.20 1.65 9 2.17 23.40 11.66 lo 2.83 23.60 2.90 23.80 12 3.00 24.00 11.72 13 3.00 2.4.20 111.74 14 2.4.40 15 3.30 2.4.60 1.72 16 13.43 24.80 1.78 17. 25.00 11 se 18 5.82 25.20 7.81 19 14.32 25.90 11.82 NQ OH PH achledem 25.60 11. 84 25 80 25.00 11. 85 26.20 Z 26.40 26.00 89 26, 801 I. 90 27 2.7.20 1.92 27.40 1.93 27. 66 11.94 2.7.20 195 28 12-06 3.98 12.02 68 1.70 3.19 11.76 33 3.61 34 12.07 12.09 12.12 12.13 12.15 100 35 36 37 12.12 61 38 39 40 12.19 12 2.0 12 21 pH at half equavilant point =pka You are required to perform the following tasks before you leave the test: NaOH = 0.1 moldms 1. Plot a suitable pH titration graph. Hence determine (a) The concentration of the unknown acid (b) The acid dissociation constant -pka 2. Determine a value for the cell constant. ka-10 D F G G H K 14 12 . . . o . . lo 9 10 00 8 pH 6 4 . . O Series "pH" Point 19" (19.4.32) O . . O . . O O N 2 o 0 45 40 35 5 0 15 10 Volume NaOH added tm3