The rocket widget for Guinness is made using a $12-$step process with task names and durations $($in minutes$)$ as shown in the following

goal of the line is to produce $40$ rocket widgets in an $8-$hour shift.

Use the longest operation time to assign tasks to workstations. What is the theoretical minimum number of stations?

a$.6$

b$.7$

c$.9$

d$.8$