Sorry, but I need to ask another clarifying question.
Mcrit is one of those terms which has been applied to a number of areas.
One definition refers to the Mach number at constant lift coefficient where the drag rise is a certain level above the drag level at .7M
The assumption is that .7M represents the incompressible level.
This definition is related to Long Range Cruise Mach (LRC) on the real airplane and is weight related.
Another definition is associated with the airplane's defined Mmo/Md speeds. These are in fact also weight related, but to keep things simple are given a single value.
Which one interests you?