The area of the pond is
Area = l * w
Area = 50 * 50
Area = 2500 square meters.
Then there is a sidewalk with 5 meters wide around the pond.
So the new dimension is
60 * 60
Area = 60 * 60
Area = 3600
Then at 45 m^2 = $74
= 3600 / 45 * 74
= $5,920
So the total cost of tile is $5,920.