statisitics problems

I have two questions that I need help with:1. a. For what value of c is the quantity sum(x_i - c)^2 minimized? b. using the result of part (a), which of the two quantities sum(x_i - (x bar))^2 and sum (x_i - mu)^2 will be smaller than the other (assuming (x bar) does not equal to mu)2. consider the following information about travelers on vacation: 40% check work email, 30% use a cell phone to stay connected to work, 25% bring a laptop with them, 23% both check work email and use a cell phone to stay connected, and 51% neither check work email nor use a cell phone to stay connected nor bring a laptop. in addition, 88 out of every 100 who bring a laptop also check work email, and 70 out of every 100 who use a cell phone to stay connected also bring a laptop. a. what is the probablitiy that a randomly selected traveler who checks work email also uses a cell phone to stay connected?b. what is the probability that someonw who brings a laptop on vacation also uses a cell phone to stay connected?c. if the randomly slected traveler checked work email and brought a laptop, what is the probability that he/ she uses a cell phone to stay connected?Thank you so much!!!