To rent a kayak and a paddle, there is a fixed fee to use the paddle, plus a charge of $\$ 5$ per hour to use the kayak. For a three hour rental, the total cost is $\$ 30$. What is the total cost for a six hour rental?
(A) $\$ 50$
(B) $\$ 15$
(C) $\$ 45$
(D) $\$ 60$
(E) $\$ 90$
The total cost to use the kayak for 3 hours is $3 \times \$ 5=\$ 15$. Since the total rental cost for 3 hours is $\$ 30$, then the fixed fee to use the paddle is $\$ 30-\$ 15=\$ 15$.

For a six hour rental, the total cost is thus $\$ 15+(6 \times \$ 5)=\$ 15+\$ 30=\$ 45$.

ANsWeR: $(\mathrm{C})$