38 people were asked if they have visited Thailand, Brunei or
Indonesia before. Four of them have been to all of the countries. Eight have been
to Thailand and Brunei, 15 have been to Brunei and Indonesia, and 11 have been
to Thailand and Indonesia. Given that 18 had been to Thailand, 19 to Brunei, and
26 to Indonesia, illustrate the above information on a clearly labelled Venn diagram.
Hence, find out how many people have visited
a) one of the three countries only;
b) more than one of the three countries;
c) Thailand or Indonesia;
d) none of the three countries.