Identify the error that exist in this method program:

public static double $f1($double basic, double hour$)\{$

if $($basic $1000)$

extra $=$ basic ${?}^{**}$ hour ${?}^{**}0\mathrm{.}3$;

else if$($point $2000)$

extra $=$ basic ${?}^{**}$ hour ${?}^{**}0\mathrm{.}4$;

else

extra $=$ basic ${?}^{***}$ hour ${?}^{***}0\mathrm{.}5$;

return extra;

$\}$

Your answer:

Wrong method header

Variable extra is unknown

A wrong use of hour data type

No error