programming in C Language

1)      Write the output of the following segment of code. Do it using pencil and paper

typedef char* string;

            char msg1[]= {"There will be no quiz next week. Hooray!"};

            char msg2[]= {"Thank you. I don't have to study CSCI610"};

            string str1,str2,str3,str4,str5,str6;

            str1 = strrchr(msg1,'n');

            str2 = strchr(str1,'H');

            *(str2-1)='\0';

            str3= strchr(msg1,'T');

            str4= strchr(str3,'q');

            *(str4-4)=*(str4+4)='\0';

            printf( "%s a %s %s\n",str3, str4, str1);

            str5 = strchr(msg2,'I');

            str6 = strrchr(msg2,'h');

            *(str5+1) = '\0';

            strcpy(msg1, str6);

            printf( "%c %s!\n", *str5, msg1);

All I want just the output of this and what does the follwing mean : 

*(str4-4)=*(str4+4)='\0';

 *(str5+1) = '\0';

*(str2-1)='\0';