(If you are curious how this mistake got there - it comes from a previous version of EC-EVAL. In the older version, the arguments are processed one at a time but CONSed onto the front of argl. This had the nasty effect of leaving the actual argument values in argl in reverse order. In the newer EC-EVAL code (discussed in the book and the handout) ADJOIN-ARG is used to put argument values onto the end of argl -- which is much cleaner.)
I have posted solutions so you can check your answers. You really should work through the procedures and problems on your own, and only use these solutions to check your answers.