$10 X + $6 Y = $2000 equation 1

10X represents both the top and bottom cost of the fence, and 6Y is the cost of both sides of the fence. We want to use up the entire 2000 dollars.

Isolating Y we have Y = --1.67X + 333.33

Multiply X and Y to get --1.67X^2 + 333.33X

Differentiate to get --3.34X + 333.33, and equate this to zero.

Solve for X to get --333.33 / --3.33 = 100 feet

Plug this into equation 1 and solve for Y to get 166.67 feet.

So we have X = 100 Feet, and Y = 166.67 Feet

Area will be X times Y or 16,667 square feet.

Top and bottom fencing will cost $1000, sides will cost $1000.

10X represents both the top and bottom cost of the fence, and 6Y is the cost of both sides of the fence. We want to use up the entire 2000 dollars.

Isolating Y we have Y = --1.67X + 333.33

Multiply X and Y to get --1.67X^2 + 333.33X

Differentiate to get --3.34X + 333.33, and equate this to zero.

Solve for X to get --333.33 / --3.33 = 100 feet

Plug this into equation 1 and solve for Y to get 166.67 feet.

So we have X = 100 Feet, and Y = 166.67 Feet

Area will be X times Y or 16,667 square feet.

Top and bottom fencing will cost $1000, sides will cost $1000.

Use this logic and format to solve for your other questions( b and c).