Question

A 0.3 ml dose of a drug is injected into a patient steadily for 0.65 seconds. At the end of this time, the quantity, , of the drug in the body starts to decay exponentially at a continuous rate of 0.35 percent per second. Using formulas, express as a continuous function of time, , in seconds.

Answer 1

Use the compound interest formula: A=P(1+i)^t.

P is the initial amount of the drug, 0.3ml.
i is - 0.0035.
t is in seconds.

You'll get:
A=0.3(1-0.0035)^t.

Sub in any value on t to find out how many ml are left t seconds after injection.

The 0.65 second injection time does not seem to be relevant as the question clearly states that the exponential decay starts AFTER the injection is completed.