Answer
$\color{blue}{\bf{\text{(a)}A=36.525x}}$
$\color{blue}{\bf{\text{(b)}2629.8\text{mg}}}$
Work Step by Step
$0.05$mg per liter, $2$ liters per day, $365.25$ days per year, times $x$ years
gives us $A$ mg lead over $x$ years
$A=(0.05)(2)(365.25)(x)$
$\color{blue}{\bf{A=36.525x}}$
if a person lives to 72 years average, than
$A=36.525(72)$
$A=2629.8$mg
$\color{blue}{\bf{2629.8\text{mg}}}$
