An assembly line is assigned as follows. Station 1- task A, B, and C. Station 2- task D. Station 3- task E and F. The task times are 7, 3, 2, 9, 4, and 5 minutes respective to A, B, C, D, E, and F. (Assume that there is no precedence relationship between the tasks, i.e., they can be performed in any order). Calculate the efficiency.