I was wrong
I repeated the problem.
This is what I did.
I took some points from the graph and I evaluated the equations (the x value) to optain the "y" and I'm compared the result of the equation with the data of the points, for example
Equation 1
y = 500x + 34570
Data from the graph: (1, 35250)
y = 500(1) + 34570
y = 35070
Comparing 35070 is close to 35250
other point: (2, 35600)
y = 500x + 34570
y = 500(2) + 34570
y = 35570
Comparing
35570 is close to 35600
final point: (6, 37450)
y = 500(6) + 34570
y = 3000 ´+ 34570
y = 37570
Comparing
37570 is close to 37450
I repeated this process with the three equations given, and the one that showed the closest values was the first one.
So, the solution is the first choice