package InterestAccount;
use strict;
use warnings;
use base 'BankAccount';

sub new {
   my $class = shift;
   my ($name, $acct, $bal, $rate) = @_;

   my $self = $class->SUPER::new($name, $acct, $bal);

   $self->{rate} = $rate;
   return $self;
}

sub accrue {
   my $self = shift;

   $self->{balance} *= (1 + $self->{rate});
}

1;