The Monthly Cost of Driving a Car Depends on the Number

Short Answer

The monthly cost of driving a car depends on the number of miles driven. Julia found that in October it cost her $\$ 200$ to drive $300 \mathrm { mi }$ and in July it cost her $\$ 350$ to drive $600 \mathrm { mi }$ . Express the monthly cost $C$ as a function of the distance driven $d$ assuming that a linear relationship gives a suitable model.