Generally, q/a is on formal or informal basis. At both request levels as many questions as possible are asked each time AI is requested. Believe it or not both can accour in the same time frame.
Approval given will at least allow sales, even if additional testing/followup is required. Follow on tools should have much less time in review, but may need add. study. These studies can be simple to conduct in the ongoing marketing of the product.
For example, if the FDA were to say, the 450+ lung resects done up till midyear last year, needed add., while that is a goodly number, LTC would need to do as many as the FDA required for a "study" to be complete.
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