Dear Alec: Thank very much you for the help. I revised the code according to your suggestion. The code can be interpreted by Maple this time. But when I input "Prob1(5,5,20);", an error message showed "Error, (in Prob1) illegal use of a formal parameter". What is wrong in my code this time? It seems to me the space here is too small to display all of the code. so I updated the first post and put the revised code in the first post on the top.

Dear Alec: Thank very much you for the help. I revised the code according to your suggestion. The code can be interpreted by Maple this time. But when I input "Prob1(5,5,20);", an error message showed "Error, (in Prob1) illegal use of a formal parameter". What is wrong in my code this time? It seems to me the space here is too small to display all of the code. so I updated the first post and put the revised code in the first post on the top.