can someone please tell me how do you calculate Specificity and sensitivity from AUC. thank you.
There is no single sensitivity (or specificity) value associated with a particular ROC curve's AUC.
We define an ROC curve using a range of true positive rate (sensitivity) values and their associated false positive rate. Therefore the value of the ROC-AUC does not imply a particular sensitivity (or specificity) value. There are some heuristics for selecting the optimum cut-off point for a ROC curve (e.g. the Youden index) and that cut-off point will correspond to a unique value of sensitivity (and it's respective specificity) but once more that will not map uniquely to that ROC curve's AUC.