What header files are recommended in the following program segment, and what is the output?

$//$

using namespace std;

int main$()$

$\{$

double amount $=89\mathrm{.}7$;

cout $<<$ fixed $<<$ showpoint $<<$ setprecision$(1)$;

cout $<<$ setw$(8)<<$ log$($amount$)<<$ endl;

return $0$;

$\}$