The Mad Scientist is right, and it shows how complex even a simple question can become. For the JAA exams it is usually assumed that Vmca is lower than Vmcg because of the old CAA specimen graphs for the L1011.
One of these, shown above, gives the values for Vmcg and 1.05Vmca at different density altitudes. It is then a simple matter to remove the 1.05 factor to compare the speeds.
In the example above Vmcg shows as 110.5kt, 1.05Vmca as 112kt and therefore Vmca is 106.5kt, 4kt lower than Vmcg.