Answer
(a) $8.34$
(b) $8.34$ mg
Work Step by Step
(a) The slope of the graph of $c$ is $0.0417D$. Notice that when we expand the parentheses, $c=0.0417Da+0.0417D$, where $a$ is the independent variable and $c$ is the dependent variable. When $D=200$, the slope is $0.0417\times200=8.34$
(b) For a newborn, $a=0$. Therefore, $c=8.34\times0+8.34=8.34$ mg.
