Part A:
Ans: Mass=14.11 g.
Given:
The volume of acetone, V=17.96 mL.
We know, the density of acetone, D=0.7857 g/mL.
The mass in grams of acetone is,

Therefore, mass of acetone in grasm rounded upto four significant figures is 14.11 g.
Mass=14.11 g.
Part B:
Ans: V=9.42 mL
Given
The mass of acetone, M=7.4 g.
We know, the density of acetone, D=0.7857 g/mL.
The volume in mL of acetone is,

Therefore, voulme of acetone in mL rounded upto three significant figures is 9.42 mL.
Volume, V=9.42 mL