Math queston answer please?

Question

A drug suspension (200 mg/ml) decays by zero-order kinetics with a reaction rate constant of 0.8 mg/mL/hour. What is the concentration of intact drug remaining after 2 days (48 hours), and what is its t 1/2?

Answer 1

1 hr=0.8

48 hr = 0.8x48= 38.4

intact drug after= 200-38.4 = 161.6mg/ml