Answer
(a) The horizontal asymptote is y=0. As time increases the concentration will practically disappear.
(b) See below.
(c) About 42 minutes.
Work Step by Step
(a) If the degree of the denominator is greater than the degree of the numerator, as is the case here, the horizontal asymptote is y=0. As it happens with most things we intake, there will be a spike that prompts the body to stabilize to conditions before the intake.
(b) Used a graphic calculator.
(c) The calculator approximated $t$ to about 0.71. Multiplying that number by 60 gives the answer in minutes.
