w$($a$,$ h$)$ pounds is the weight of a person who is a years old and h inches tall. What is the rate$-$of$-$change of weight with respect to height?

$($a$)$ Write the mathematical notation for the partial rate$-$of$-$change function needed to answer the question posed.

$?$a$$h$$w $?$a$$h$$w

$($b$)$ Write the units of measure for that rate$-$of$-$change function.

inches per poundpounds per inch$$inches per yearyears per inchpounds per person