Chapter 1 - Section 1.12 - Modeling Variation - 1.12 Exercises - Page 128: 37

$(a)$ $P=ks^3$ $(b)$ $k=0.012$ $(c)$ $P= 324watts$

$(a)$ According to the problem, we have $C=ks^3$ Where $k$ is the constant of proportionality. $(b)$ $P=96 watts$ $s=20mi/h$ $k$ is unknown $96=k\times20^3$ $8000k=96$ $k=0.012$ $(c)$ $s=30mi/h$ $P$ is unknown $P=0.012\times27000 = 324watts$