Does the code work?
The output looks good.

Example 1 Chapter 2

OBS    SCORE    ID    GRADE

 1       55      1      F
 2       65      2      D
 3       74      3      C
 4       76      4      C
 5       88      5      B
 6       92      6      A
 7       94      7      A
 8       96      8      A
 9       98      9      A

The log is unremarkable.