单项选择题

Questions refer to the following graph.

If every student who was in the eleventh grade in 1996 and who used a computer in school at least once a week used a computer at least once a week in 1997, and if 20% of those students who were in the eleventh grade in 1996 and who did not use a computer in school at least once a week, did use a computer in school once a week in 1997, then what percent of twelfth-graders in 1997 used a computer in school at least once a week