K. 452. A silo for storing winter food for cattle is attached to one corner of a rectangular stable. The silo is shaped like a regular triangular prism, with base edges of length 3 metres. The longer side of the stable is 9 metres. With a 9-metre-long rope, a goat is tied to the point where the silo joins with the stable (see the figure). The goat cannot break the rope, and the rope will not stretch. The buildings are surrounded with grass, and there is no fence or any other obstacle hindering the goat from grazing. Find the area that the goat can graze.
This problem is for grade 9 students only.
Deadline expired on 10 March 2015.