He cut altogether each month 30000 square .
Without knowing the size of the park, it is difficult to say how many square yards of grass David will cut altogether each month.
However, we can make an estimate based on the scale shown in the image.
The scale shows that the park is 50 yards wide and 300 yards long.
This means that the park has a total area of 50 * 300 / 2 = 7500 square yards.
Assuming that David cuts the entire park each time he cuts the grass, he will cut a total of 7500 * 4 = 30000 square yards of grass each month.
However, it is likely that there are some areas of the park that David does not need to cut, such as paved areas or areas with trees.
This means that the actual amount of grass that David cuts each month is likely to be less than 30000 square yards.