Trigger:When Case is generated then send Mail to Relevant Contact Email

trigger SendEmailTOCustomer on Case (after insert) {
    string e;
    if(Trigger.IsInsert){
      for(case b:trigger.new){
      ID d=b.contactid;
      contact con=[select name,email from contact where id=:d];
      system.debug('3333333333333333333333333'+con.email);
      e=con.email;
       Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
               String[] toAddresses = new String[] {e};
               mail.setToAddresses(toAddresses);
               mail.setSubject('New Record Is Inserted');
               mail.setBccSender(false);
               mail.setUseSignature(false);
               mail.setPlainTextBody('hi padam');
               Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
      }
    }  
}