Nathan is out rafting. He rafts 16 miles with the river current. At the end of 16 miles, he turns around and rafts the same distance against the river current. The journey takes him 4 hours overall. If he can raft at a speed of 9 mph in still water, what is the speed of the current of the river he is in? a. 5 mph
b. 6 mph
c. 4 mph
d. 3 mph

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?