Search and replace Shell Script

Had to parse 100's of files in a loop and replace a word
called Bombay with a new word Mumbai

cat file1.dat
city name is Bombay and country is INDIA.

To:
cat file1.dat
city name is Mumbai and country is INDIA.

for file in /tmp/a /tmp/c /tmp/b ; do
sed 's/Bombay/MUMBAI/g' ${file} > ${file}.new
done