What is the ruling on the prescribed waiting period (iddah) for a widow over sixty?

The 'iddah (waiting period) for a woman whose husband has died is four months and ten days, whether she is young or old, based on the Almighty's saying: "And those of you who die and leave wives behind them, they (the wives) shall wait (as regards their marriage) for four months and ten days." (Quran 2:234) This is unless she is pregnant, in which case her 'iddah is until she delivers her child, based on the Almighty's saying: "And for those who are pregnant, their term is until they deliver their burdens." (Quran 65:4)