Smartphone adoption among American teens has increased substantially, and mobile access to the Internet is pervasive. One in four teenagers are “cell mostly” Internet users— that is, they mostly go online using their phone and not using some other de-vice such as a desktop or laptop computer. (Source: Teens and Technology 2013, Pew Research Center, bit. ly/101ciF1.) If a sample of 10 American teens is selected, what is the probability that 

a. 4 are “cell mostly” Internet users?

b. At least 4 are “cell mostly” Internet users?

c. At most 8 are “cell mostly” Internet users?

d. IF you selected the sample in a particular geographical area and found that none of the 10 respondents are “cell mostly” Internet users, what conclusions might you reach about whether the percentage of “cell mostly” Internet users in this area was 25%?