Textbook: concept of programming language 11th edition..

I saw the soultion in textbooks sultions at chegg but it didnt make sense

5. Modify the lexical a 4.2 to recognize the fol- lowing list of reserved words and return their respective token codes for (FOR_CODE, 30), if (IF_CODE, 31), else (ELSE_CODE, 32), while (WHILE_CODE, 33), do (DO_coDE, 34), int (INT_CODE, 35), float (FLOAT-CODE, 36), switch (SWITCH-CODE, 37). 5. Modify the lexical a 4.2 to recognize the fol- lowing list of reserved words and return their respective token codes for (FOR_CODE, 30), if (IF_CODE, 31), else (ELSE_CODE, 32), while (WHILE_CODE, 33), do (DO_coDE, 34), int (INT_CODE, 35), float (FLOAT-CODE, 36), switch (SWITCH-CODE, 37)