Plotting the direction field of a differential equation

I have to sketch the direction field for the following differential equation:

$$\frac{dy}{dx}=\frac{-0.02 y +0.00002 xy}{0.08 x-0.001xy}$$

This is the code I used, which gives an incorrect plot:

StreamPlot[Normalize[{1, (y (-0.016 + 0.00008 x))/(x (0.12 - 0.006 y))}], 
    {x, -200, 200}, {y, -200, 200}, Axes -> True]

The following picture shows what I need to get:

enter image description here

Answer

I believe this is getting close to what you want:

f[x_, y_] := (-0.02 y + 0.00002 x y)/(0.08 x - 0.001 x y)

VectorPlot[{1, f[x, y]}, {x, 0, 3100}, {y, 0, 150}, VectorStyle -> Arrowheads[{}]]

enter image description here

Comments

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