1. A person with kidney failure received regular dialysis treatment for 17 days. Fig. 2.2 shows how the concentration of urea in the blood changed over the 17 days. 250 200 150 concentration of urea in the blood 100- mg per dm³ 50 0 8 9 10 11 12 13 14 15 time days 16 17 (a) State how many times the person received dialysis treatment.
(b) Calculate the decrease in the concentration of urea in the blood from the beginning of dialysis until the end of the treatment. ​