According to a recent study, cell phones, especially text messaging, is the main medium for teenagers to

Question:

According to a recent study, cell phones, especially text messaging, is the main medium for teenagers to stay connected with friends and family (CNN, March 19, 2012).
It is found that only 23% of teens don’t own a cell phone. Of those who own a cell phone, only one in four uses a smart-phone. What proportion of all teenagers use a smart-phone?