Answer:
Part a : After next day in noon it will be 59.53 mg
Part b : After 52.53 hours it will be 35 % of initial
Explanation:
Equation is given by
A = 75(0.5)

initial dose at midnight
Part (a) then at noon next day means 12 hrs ,plugging t = 12 here ,we get

A=75(0.5)

on simplifying it ,we get
A =75(0.7937)
A=59.53 mg
Part (b) : 35 % of initial level means A = 0.35 of initial= 0.35 (75 )


t = 54.53 hours
After 54.53 hours it will remain 35% of initial amount