The cost function is given as:
[tex]C(n)=5500+175n[/tex]a)
[tex]\begin{gathered} The\text{ cost of transporting 12 tons:} \\ C(12)=5500+175(12) \\ C(12)=\text{ \$7600} \end{gathered}[/tex]b)
[tex]\begin{gathered} C(n)=5500+175n \\ \Rightarrow9525=5500+175n \\ \Rightarrow9525-5500=175n \\ \Rightarrow4025=175n \\ \Rightarrow n=\frac{4025}{175} \\ n=23\text{ tons} \end{gathered}[/tex]