Blah, Blah, Blah...

Create a function which replaces the last n words with "blah". Add "..." to the last blah.

Examples

blah_blah("A function is a block of code which only runs when it is called",  5) ➞ "A function is a block of code which only blah blah blah blah blah..."

blah_blah("one two three four five", 2) ➞ "one two three blah blah..."

blah_blah("Sphinx of black quartz judge my vow", 10) ➞ "blah blah blah blah blah blah blah..."

Notes

• If n is longer than the amount of words in the sentence, replace every word with "blah" (see example #3).
• All blahs shall be lowercase!