Isme estimated that there are 50 students in the seventh-grade class. There are actually 40 students in the seventh-grade class.
A. What is Isme's percent error?

B. Out of the 40 students in the seventh-grade, 60% of the students carry a cell phone. What fraction of the students in the seventh grade class carry a cell phone? How many students in the seventh grade class carry a cell phone/