A grocer's balance shows the mass of an object as 2.500 kg. Two gold pieces of masses 21.15 g and 21.17 g are added to the box. What is (a) the total mass in the box and (b) the difference in the masses of the gold pieces to the correct number of significant figures?

Explanation

To solve the problem step by step, we will address both parts (a) and (b) of the question.

### Part (a): Total Mass in the Box

1. **Identify the mass of the object in the box**: The initial mass \( M_i \) is given as 2.500 kg. This value has 4 significant figures.

2. **Convert the mass of the gold pieces from grams to kilograms**:
- For the first gold piece:
...