-7 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_rds(file = "data/test_1.rds") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> writing-to-a-file-8 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> write_rds(mtcars, "data/test_2.rds") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> writing-to-a-file-9 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> list.files("data