How many significant figures are present in each of the following measured quantities, and what is the uncertainty based on the convention of significant figures?
(a) A package of candy has a mass of 103.42 g.
(b) The mass of a milliliter of a gas is 0.003 g.
(c) The volume of a solution is 0.2500 L.
(d) The circumference of Earth is 24,900 miles.