Select the equivalent expression. \left(6^{-4}\cdot 8^{-7}\right)^{-9}=?(6 −4 ⋅8 −7 ) −9 =?left parenthesis, 6, start superscript, minus, 4, end superscript, dot, 8, start superscript, minus, 7, end superscript, right parenthesis, start superscript, minus, 9, end superscript, equals, question mark Choose 1 Choose 1 (Choice A) A 6^{36}\cdot 8^{63}6 36 ⋅8 63 6, start superscript, 36, end superscript, dot, 8, start superscript, 63, end superscript (Choice B) B 6^{5}\cdot 8^{2}6 5 ⋅8 2 6, start superscript, 5, end superscript, dot, 8, squared (Choice C) C \dfrac{1}{6^{13}\cdot 8^{16}} 6 13 ⋅8 16 1

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?