Определите корректное использование ключевого слова READ-ONLY 
 10 public section.
 20   Data: Price(3) type p decimals 2 
                     value 100 READ-ONLY.   
 30   Types: type_category(15)  type C READ-ONLY.
 40   Constants: write_position type I value 10 READ-ONLY.

 50  private section.
 60   data: category(15)        type C READ-ONLY,
 70   class-data: course_count  type I READ-ONLY
Endclass.