A ship travels between two ports. The cost of fuel is C=$100(ax+b/x+10)
Where x is the average speed of the ship in knots (x > 0) and a and b are constants. If the ship travels at 4 knots the cost of fuel is $9000 but at 6 knots it is $7000.
a) Form two linear equations consist of a and b.
b) Find the values of a and b.
c) If there are two ports that are 1000 knots apart, what is the cost of the fuel.