I need to write reusable oop code in C#.NET which does the following (just one solution): 1. counts occurences of a specific letter in a string. e.g 'l' in "Hello world" => 3 2. counts occurences of a specific digit in a number e.g. 2 in 2546522772 => 4 3. Adds two numbers together. e.g 2+5 => 7
Which is the best way to approach this? Thanks.