The entire area of a circle is π(r^2) = π(8^2) = 64π
There is a proportion between the area of a sector with angle x and the area of the entire circle (which covers 360°:
area of the sector / angle of the sector = area of the circle / 360°
Then, area of the sector / 300° = 64π / 360°
area of the sector = (64π / 360°) * 300° = 53.33π cm
Then, the answer is the last option: 53.3