From the given infomation, the cost for river Y is constant, that is,
[tex]\begin{gathered} Y=\text{ \$33+\$13} \\ Y=\text{ \$46} \end{gathered}[/tex]
where Y denotes the cost for river Y.
On the other hand, the cost for river Z is given by
[tex]Z=\text{ \$5}\cdot n+\text{ \$13}[/tex]
where n denotes the number of hours and Z the cost for river Z.
Therefore, the Total cost (C) will be the sum of the cost for river Y and river Z, that is,
[tex]C=\text{ \$46+\$5}\cdot n+\text{ \$13}[/tex]
which gives
[tex]C=\text{ \$5}\cdot n+\text{ \$}59[/tex]
