what's the meaning of "Good for them"? ‘I’m quite sure. I can hear one lot of bells with my left ear, and another lot with my right.’ They had still seen no one. The sparse gas lights fell on the furnishings of a stone quay, small but plainly in regular use. ‘The whole population must be ringing the bells.’ His own remark discomfited Gerald. ‘Good for them.’ She took his hand. ‘Let’s go down on the beach and look for the sea.’ Q1： Is “the whole population must be ringing the bells” an allusion or just its literal meaning? Q2: what's the meaning of "Good for them"?