The lowest possible number of researchers who will NOT be assigned to the team they prefer is 15.
How did we get this value?
Let's start by finding out how many researchers will be assigned to each team based on the given percentages.
Total number of researchers = 50
Team A (40%): 0.4 * 50 = 20 researchers
Team B (60%): 0.6 * 50 = 30 researchers
Now, let's determine the number of researchers who prefer each team.
Team A (70%): 0.7 * 50 = 35 researchers
Team B (30%): 0.3 * 50 = 15 researchers
Now, we need to minimize the number of researchers who will NOT be assigned to the team they prefer. We can achieve this by making sure that as many researchers as possible get assigned to their preferred team.
In this case, the 30 researchers who prefer Team B will all be assigned to Team B, but only 20 researchers will be assigned to Team A. Therefore, 15 researchers who prefer Team A will not get their preferred assignment.
So, the lowest possible number of researchers who will NOT be assigned to the team they prefer is 15.