On a particular system, all passwords are 8 characters, there are 128 choices for each character, and there is a password file containing the hashes of 210 passwords. Trudy has a dictionary of 230 passwords, and the probability that a randomly selected password is in her dictionary is 1/4. Work is measured in terms of the number of hashes computed. a. Suppose that Trudy wants to recover Alice's password. Using her dictionary, what is the expected work for Trudy to crack Alice's password, assuming the passwords are not salted?
b. Repeat part a, assuming the passwords are salted.
c. What is the probability that at least one of the passwords in the password file appears in Trudy's dictionary?

Imagine that you have a friend who is starting a small business and is interested in using social media to spread the word. he is not certain that it is a good move, and has come to you for . would you advise him to use social media to advertise his business? why or why not? support you answer with information from the text.

Jaina and tomas are being considered as new tenants in an apartment. the landlord looks at their creditworthiness because he wants to be sure his new tenant pays the rent on time and in full. the table below summarizes the information that was on their applications. application information questions jaina tomas how many years have you had your job? 5 2 what is your monthly salary? $1,850 $2,500 how many credit cards do you have? 4 1 how much debt do you have? $13,000 $7,000 how many times were you late with payments on credit cards in the past year? 5 1 who will the landlord decide to be more creditworthy and why? tomas because the ratio of his debt to income is less. jaina because she has had her job longer, which makes her look more stable. jaina because she has more credit cards available to her. tomas because he makes more money per month.

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?