Can you help me and explain too :)

Apatient is given 50 mg dose of medicine the medicines effectiveness decreases every hour at a constant rate of 40% what is the exponential decay function that models this scenario how much medicine will be left in the patients system after 2 hours

Which is the graph of f(x) = (4)x? image for option 1 image for option 2 image for option 3 image for option 4

What is the area of mnp? 40 m2 60 m2 68 m2 127.5 m2