I do not understand this work sheet… could you please help me

Here is the math problem: 

Speedy Movers charges its customers a flat fee of $300 and an additional $40 per hour.  write an equation to find the total cost charged in dollars, C, in terms of the number of hours needed for a move, h

These are the questions( but i do not understand the questions and i dont get how to do them) 

 A.  Equation——– (this is my answer)   Y=40x+ 300

B. graph the equation by either making a table or using the slope and Y intercept. BE SURE YOU LABEL THE x AND y AXIS AND YOUR INTERVALS!    I do not know how to graph it ( the equation)

C. how much would it cost for three hours.SHOW YOUR WORK!

D. if the cost was $700, how many hours did it take to move? SHOW YOUR WORK!

( i do not understand how to do these)