Answer
See the explanation below.
Work Step by Step
a) the cardiac output is the amount of blood pumped per unit of time.
b) An amount of dye injected is measured over time until the die has left. If $D$ is the amount of dye and $f(t)$ is the concentration and $t_e$ is the endpoint, then the output is $$\frac{A}{\int_{0}^{t_e} f(t) dt}$$