Mr. X is the director of municipality. He has been appointed 30%, 50% and 20% engineers
from countries “A”, “B”, “C”, respectively. He knowns from previous experiences that 0.02%,
0.01%, and 0.05% engineers from countries “A”, “B”, and “C” are inefficient. Recently, Mr. X
appointed 500 engineers from these three countries. After one months of working record, it
is found that an engineer is inefficient engineer. What is the probability that he was from
country “C”? Also calculate the probability that he was from country “A” or “B”?