What is the factored form of the expression?

s^4 – 16

a. (s - 2)^2(s + 2)^2

b. (s - 2)(s + 2)

c. (s - i)(s + i)(s - 2)(s + 2)

d. (s - 2i)(s + 2i)(s - 2)(s + 2)

In a test for esp (extrasensory perception), a subject is told that cards only the experimenter can see contain either a star, a circle, a wave, or a square. as the experimenter looks at each of 20 cards in turn, the subject names the shape on the card. a subject who is just guessing has probability 0.25 of guessing correctly on each card. a. the count of correct guesses in 20 cards has a binomial distribution. what are n and p? b. what is the mean number of correct guesses in 20 cards for subjects who are just guessing? c. what is the probability of exactly 5 correct guesses in 20 cards if a subject is just guessing?