In order to improve loop performance, it�s important to make sure the loop does not include unnecessary operations or statements.
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Write a method public static string getdigits(string phonenumber) that takes an 11-character phone number written with any combination of 11 uppercase letters, lowercase letters and/or digits, and zero or more hyphens, and which returns the digits that a person would have to press on a cell phone to dial that phone number. we will use the mapping of letters to digits given at en.wikipedia.org/wiki/telephone_keypad# /media/file: telephone-keypad2.svg you may assume that the string parameter phonenumber contains some combination of exactly 11 uppercase letters, lowercase letters and/or digits, but that any number of hyphens may be present. you can assume that a hyphen will not appear as the first or last character of the string. do not assum