<image>Fill in the appropriate unit in the parentheses.

(1) The area of the envelope in Figure 1 is about 200 ____;_
(2) The area of the desktop in Figure 2 is about 64 ____;_
(3) The length of the cover of the math book in Figure 3 is about ____;_
(4) The area of the playground in Figure 4 is about 3600 ____;_
(5) The area of the tablecloth in Figure 5 is 15000 ____;_
(6) The area of the double bed in Figure 6 is about 4 ____.