The Greenhouse is a golf shop inside the clubhouse of a Vermont golf course. Hayden Santos, owner of The Greenhouse, is deciding how much shelf space to devote to each of four different golf ball types. Hayden has a maximum front shelf space of $15$ feet to devote to golf balls. He wants a minimum of three feet and a maximum of seven feet of front shelf space for each golf ball type. Appropriate per$-$case data on the four ball types follow:

Distance Spin Straight Durable

Sales price per case $ $23\mathrm{.}60$ $ $23\mathrm{.}10$ $ $24\mathrm{.}20$ $ $20\mathrm{.}90$

Variable costs per case $15\mathrm{.}7015\mathrm{.}5017\mathrm{.}5014\mathrm{.}40$

Cases sold per foot of front shelf space per day $33282833$

The daily contribution per foot of front shelf space for Straight is: