Calculate the following, and write the answers with the correct number of significant figures.
20. (5.63 x 1015 m)(8.9630 x 104 m)
21. (45000 cm + 21.890 cm)(2.03 x 10-9 cm)
22. (8.36 x 1011 g) + (2 x 1010 g)
5.5790 x 100 g