A job shop manager wants to determine the proportion of time the workers are idle. The shop employs ...

A job shop manager wants to determine the proportion of time the workers are idle. The shop employs two types of workers. Type 1 includes three workers and Type 2 includes two workers.
 
  The manager suspects that the proportion of idle time is about 20 percent for Type 1 workers and 15 percent for Type 2 workers. If the manager wants a 95 percent confidence level (z = 1.96 ) and a degree of precision of + 0.05, how many trips will the observers have to take through the group?
  A) fewer than or equal to 80
  B) greater than 80 but fewer than or equal to 90
  C) greater than 90 but fewer than or equal to 100
  D) greater than 100