Fancy Trends Inc., a handbag manufacturing company, assembles handbags in an assembly line using 10 workstations. The target output for an 8-hour workday is 120 bags. The sum of the task times is 30 minutes/bag. The cycle time is 4 minutes/bag. The assembly-line efficiency is ______ .

a. 65%
b. 70%
c. 75%
d. 80%
e. 85%