Bone marrow. The inside of your bones are filled with a soft tissue called marrow. There are two types of bone marrow: red and yellow. Red bone marrow is where all new red blood cells, white blood cells, and platelets are made.
Mine is 8m x 7m (3m is 10 feet, so around 27 x 23 feet). This is normal for an Australian classroom, although there's a fair bit of variation.
45 minutes to one hour per week. The release time per classroom teacher should be a minimum of forty-five (45) minutes to an hour per week for grades TK-3 and fifty-five (55) minutes to an hour per week for grades 4-6.