Given data:
The size of a single electronic book is: 2.4 megabytes.
The total number of books is: 16
The expression to calculate the total size is,
[tex]\begin{gathered} \text{Total size= Size of one file}\times\text{ Number of books} \\ =2.4\text{ mb}\times16 \\ =38.4\text{ mb} \end{gathered}[/tex]Thus, the total size of the electronic book is 38.4 megabytes, and the correct option is option 'j'.