Calculus
posted by Ethan .
The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May it cost her $410 to drive 300 mi and in June it cost her $470 to drive 600 mi. (a) Express the monthly cost C as a function of the distance driven, d, assuming that a linear relationship gives a suitable model. (b) Use part (a) to predict the cost of driving 1200 miles per month. (c) Draw the graph of the linear function. What does the slope represent?

Where are you stuck Ethan? Show me what you have so far and I'll point you in the right direction.
Hint: Draw a graph for yourself, designate the x axis as miles and the y as dollars. So when x is 300 what is y? And when x is 600 what is y? This might help you understand the question. 
I'm stuck at part a, I don't know what the function would be