Question 1201500
<font color=black size=3>
It will depend on what layout the farmer goes with.


Are the plots laid in a single straight line (configuration A)?
Or are the plots in a 2x2 grid (configuration B)?


-----------------------


Configuration A:
{{{
drawing(300,300,-5,5,-5,5,
line(-4,-1,-4,1),line(-4,1,4,1),line(4,1,4,-1),line(4,-1,-4,-1),line(-2,1,-2,-1),line(0,1,0,-1),line(2,1,2,-1),
locate(-2.96,1.6,"x"),locate(-0.96,1.6,"x"),locate(1.04,1.6,"x"),locate(3.04,1.6,"x"),locate(-2.96,-1.3,"x"),locate(-0.96,-1.3,"x"),locate(1.04,-1.3,"x"),locate(3.04,-1.3,"x"),locate(-4.58,0.2,"y"),locate(4.22,0.34,"y")
)
}}}


Perimeter = sum of exterior sides
Perimeter = 8x+2y
8x+2y = 6000
2(4x+y) = 6000
4x+y = 6000/2
4x+y = 3000
y = -4x+3000


area of one plot = xy
area of four plots = 4xy
area of four plots = 4x(-4x+3000)
area of four plots = -16x^2+12000x


We wish to max out this area.
Use a graphing tool such as GeoGebra or Desmos to graph the parabola. 
The vertex is located at (375,  2250000)
This is the highest point on the parabola.


This means a single plot that has horizontal width of x = 375 meters leads to a total max area of 2,250,000 square meters. 
This applies only if configuration A is used.


The y value would be
y = -4x+3000
y = -4*375+3000
y = 1500


Each smaller plot is 375 meters by 1500 meters.
area of one plot = 375*1500 = 562,500 square meters
area of four plots = 4*562500 = 2,250,000 square meters


-----------------------


Configuration B:
{{{
drawing(300,300,-5,5,-5,5,
line(-2,-2,-2,2),line(-2,2,2,2),line(2,2,2,-2),line(2,-2,-2,-2),line(-2,0,2,0),line(0,2,0,-2),
locate(-1.28,2.6,"x"),locate(0.72,2.6,"x"),locate(-1.28,-2.1,"x"),locate(0.72,-2.1,"x"),locate(-2.5,1,"y"),locate(2.1,1,"y"),locate(-2.5,-1,"y"),locate(2.1,-1,"y")
)
}}}

Perimeter = sum of exterior sides
Perimeter = 4x+4y
4x+4y = 6000
4(x+y) = 6000
x+y = 6000/4
x+y = 1500
y = -x+1500


area of one plot = xy
area of four plots = 4xy
area of four plots = 4x(-x+1500)
area of four plots = -4x^2+6000x


Follow similar steps as the previous configuration.
This time the vertex is located at (750,2250000)
This means a horizontal width of x = 750 leads to a max area of 2250000 square meters.
This applies only if configuration B is used.


y = -x+1500
y = -750+1500
y = 750


Each smaller plot is 750 meters by 750 meters.
area of one plot = 750*750 = 562,500 square meters
area of four plots = 4*562500 = 2,250,000 square meters



--------------------------------------------------------
--------------------------------------------------------


Summary:


Configuration A has each smaller plot of 375 meters by 1500 meters.
Configuration B has each smaller plot of 750 meters by 750 meters.


Both configurations lead to a max total area of 2,250,000 square meters when considering all four plots.
</font>