Let the dimension of the rectangular lot be
x and
y
x = sides parallel to water
y = sides perpendicular to water
Perimeter
$2x + 2y = 1000$
$x + y = 500$ ← Eq. (1)
Cost of fence
$25x + 5(2y) = 9500$
$5x + 2y = 1900$ ← Eq. (2)
Equation 2 - 2 × Equation (1)
$3x = 900$
$x = 300 ~ \text{ft}$
From Equation (1)
$300 + y = 500$
$y = 200 ~ \text{ft}$
Answer = 300 ft × 200 ft → [ D ]
