The caffeine content in a 10-ounce mug of percolated coffee is approximately 100 milligrams. So, two 10-ounce mugs would provide:
\[
2 \times 100 = 200 \, \text{milligrams}.
\]
A 12-ounce cup of a caffeinated soft drink contains approximately 40 milligrams of caffeine.
Thus, the total amount of caffeine consumed per day is:
\[
200 \, \text{mg} + 40 \, \text{mg} = 240 \, \text{mg}.
\]
The minimum amount of caffeine is therefore approximately **190 milligrams**.
Final Answer:
\[
\boxed{\text{The correct answer is (B) 190.}}
\]