Correct statements of similarities and differences between calling user defined functions and library functions are:

a) Similarity: A call to either requires the function name followed by parenthesized
comma separated list of arguments that match the prototype in number and type.
b) Difference: Library functions require inclusion of header files for declarations but
user defined functions do not require any declaration before use.
c) Similarity: Either library or user defined functions may be value returning or void functions.
d) Difference: Library functions all provide a return value, user functions must be
void functions.
e) Difference Library function declarations (sometimes definitions) come from
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