The Star General Hospital utilizes Kanban cards to optimize its operational processes, particularly in one of its high-traffic medical stations where medical supplies are consumed at a rate of 350 units per hour. Each standard container holds 40 units of medical supplies, and the Kanban system is designed with a cycle time of 30 minutes. Currently, the hospital employs 5 Kanban cards in this process, and the system is functioning effectively. What safety factor was applied in this case?

a) 0.125 

b) 0.143 

c) 0.156 

d) 0.191