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2. Macros are available in most high-level programming languages. The body of a macro is simply used to replace a macro-call during the preprocessing stage. A macro introduces a "true inline" function that is normally more efficient than an "out-line" function. However, macros suffer from the side-effect, unwanted, or unexpected modifications to variables. Macros should be used cautiously. The main purpose of the following programs is to demonstrate the differences between a function and a macro. Observe each of the functions below, written in C, and understand their functionality. You can use either GNU gec under Unix or Visual Studio to implement the code in this question. 2.1. Write, in C, four macros to re-implement the given four functions. Name them: subm, squared_addm, smallerm, and evenm, respectively. [40 points]