Y=cos(2x+pi) - 2
y= - cos(2x) - 2
{ Since cos(x+pi) =-cos(x)}
Area of field=xy=5000
perimeter of field=2(x+y)300
x+y=150
x=150-y
y(150-y)=5000

solve it
u get y= 50 or 100
then x=100 or 50
therefore the dimensions are 100m and 50m
Fill in (2) in (1):
a=cca => c^2=1 => c=+1 or c=-1
Fill in (3) in (2)
b=aba => a^2=1 => a=+1 or a=-1
same for (1) in (2): b=+1 or b=-1
To satisfy all conditions at the same time, a, b and c all have to be +1 OR any two of them must be negative (e.g., a=b=-1, c=+1).
In all cases, abc=1
973.2 is the answer to your question