Provide explanations for the following:

1. Why does 5060 have three significant figures?

2. Why 5.67 + 0.00032 = 5.67 (and not 5.7 or 5.67032 or any other number).

3. Why does 4.03/0.0000035 = 1.2 x 106, instead of a different number of significant figures?

4. Why is it that 85.48 rounded to two sig. figs. is 85 and not 86?

5. What is an "exact number"?