Processes A, B, C, and D are all used to produce seafood gumbo with seemingly infinite demand. The steps feed directly into one another, so A's output goes to B, and B's output goes to C, and finally, C's output goes to D. Process A can produce 400 units per minute, Process B can produce 300 units per minute, Process C can produce 300 units per minute, and Process D can produce 400 units per minute. Which process step(s) can experience idle time while the overall process still maximizes output? a. Processes B and C b. Processes A and D c. Process A d. Process D