Which of the following should be done in order to prepare 0.40 M NaCl starting with 100 ml of 0.30 M NaCl (mol.wt. of NaCl = 58.5)?

$$\begin{gathered} 100\mathrm{ml}\text{. of }0.30\mathrm{M}=\frac{100\times 0.3}{1000}=0.03\text{ mole of }\mathrm{NaCl} \\ 100\mathrm{ml}\text{ of }0.40\mathrm{M}=\frac{100\times 0.4}{1000}=0.04\text{ mole of }\mathrm{NaCl} \\ \text{ Moles of }\mathrm{NaCl}\text{ to be added }=0.04-0.03=0.01\text{ mole = 0.585 gm} \end{gathered}$$