複選題24. After people take the medicine X, it can be absorbed into the body through pathway A→B and enter the blood. Medicine in the blood can reduce its concentration through decomposition (B→C) or excretion (B→D), as shown in the figure below: Assume that the process A→B is much faster than those of B→C and B→D. Therefore, each time a medicine with a dose of [X]o is taken, it can be regarded as immediately producing a concentration of [X]b (= 0.020 mM) of X in the blood. Assume that B→C and B→D are both first-order processes, and their rate constants are k1 (= 0.075 h-1 ) and k2 (= 0.025 h-1 ), respectively. If a person takes the same dose ([X]o) of the medicine every t hour, answer the following questions. (A) Just after taking the medicine for the nth time, its concentration in the blood is equal to [P]n. Express [P]n as a function of [X]b, k1, k2 and t. 3% (B) Continue to take the medicine every 6 hours for a long period of time (n→∞), calculate [P]∞ (in mM)? 3% (C) Find the half-life of the medicine in the blood. 2% (D) What proportion of the decrease in medicine concentration in the blood is caused by decomposition? 2%