How to reduce the first letter in certain words in a sentence?

Question

ruby

There is a certain variable sentences that contains an expression where random words can be capitalized, how can you make the words Andand Ofchange the first letter in this variable to a small one, unless of course they are available.
Example

sentences = "The Department Of Higher Education And Workforce"

should become
"The Department of Higher Education and Workforce"

Answer 1

words = [ 'and', 'of' ]

sentences.gsub!(/\b(#{words.join('|')})\b/i) {|m| m.downcase}