foo.c: In function 'main':
foo.c:15:39: error: 'static_cast' undeclared (first use in this function)
   15 |                 price = (double)((a / static_cast<double>(20) - m) * k);
      |                                       ^~~~~~~~~~~
foo.c:15:39: note: each undeclared identifier is reported only once for each function it appears in
foo.c:15:51: error: expected expression before 'double'
   15 |                 price = (double)((a / static_cast<double>(20) - m) * k);
      |                                                   ^~~~~~

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