9. Solving a chemistry problem

2 The concentration of the stock Ni2 standard solution was 10 mg/mL. In a series of standard solutions, different volumes of this solution (Vml) were taken, reagents were added, and the solutions were diluted to 50 ml
V(ml) 1 2 4 8
h(mm) 17 34 68 136
For analysis, 2.5 ml of the test solution was taken; after adding the reagents and diluting to 50 ml, the wave height of the resulting solution was 82 mm. Calculate the concentration of the test solution.