If the recommended adult dosage for a drug is $D$ (in mg), then to determine the appropriate dosage $c$ for a child of age $a,$ pharmacists use the equation $$c=0.0417 D(a+1)$$ Suppose the dosage for an adult is $200 \mathrm{mg}$.
a. Find the slope. What does it represent?
b. What is the dosage for a newborn?