Below you are shown a product structure tree for end item A. Weekly lead time values for purchase, manufacture, and assembly activities are shown to the immediate right of each item identifier. What is the minimum length planning horizon that should be considered for MRP production scheduling? A 2 to B 5 2 D 4 E 3 F 2 G 3 H 2 Select one: O a. 6 weeks O b. 5 weeks O c. 4 weeks O d. 23 weeks O e. 7 weeks