We have been given that 15 people can comfortably stand in a section that is 5ft by 8ft .
Hence, the area of this section is given by

Hence, we can say that 15 people can comfortably stand in an area 40 square feet.
Now, we know that 1 yard is equal to 3 feet.
Hence, the area of the section 400yds by 200 yds is equal to

Now, in 40ft^2, 15 people can stand comfortably.
Hence, in 720000 ft^2, number of people can stand comfortably is

Therefore, 270000 people can stand in the park of dimension 400 yds by 200 yds