You are given the set of letters { A, B, C, D, E } . How many three-letter strings (i. e., sequences of 3 letters) can be made out of these letters if each letter can be used only once? (In this and subsequent questions, your answer should be a number. Do not enter ‘!' or combinations in your answer.)

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.