Question 4. Suppose that the distances of javelin throws of professional athletes follow approxi- mately a normal distribution with mean 310 ft and standard deviation 4 ft. (a) What is the minimum distance thrown by someone who belongs to the top 10% of the athletes? (b) What percent of the athletes throws the javelin farther than 319 ft? (c) Consider a competition with 20 javelin throwers. Suppose that the javelin throwers are mutually independent of each other. What is the probability that the winner has thrown the javelin 313 to 323 ft far? (Hint: Express the probability in terms of the distribution function I of a standard normal random variable, then use R to compute the values. )