Rewrite the statements in each of the following arguments in "if-then" form. Then, use symbols to represent the form of the argument and tell whether it is valid or invalid. Example: All movies directed by Alfred Hitchcock have suspensefül plots. The movie North by Northwest has a very suspenseful plot. Therefore, North by Northwest was directed by Alfred Hitchcock.
Answer: If a movie was directed by Alfred Hitchcock, it has a suspenseful plot. If the movie is North by Northwest, it has a very suspenseful plot. Therefore, if the movie is North by Northwest, it was directed by Alfred Hitchcock. The form of this argument is $a \rightarrow b$
$c \rightarrow b$
Therefore, $\quad c \rightarrow a$
The argument is not valid.
All donkeys have long ears. All long-eared creatures are habitual eavesdroppers. Therefore, all donkeys are habitual eavesdroppers.