10-month-old boy presents high fever and watery，bloody，mucous diarrhea for 3 days，vomiting and anuria for 24 hours with a paternal complaint of "refusing to eat and sleeping too much".Physical examination reveals a lethargic boy with a body temperature of 39℃，deeply sunken eyes，dry mucosa and poor skin turgor.His extremities are cool with capillary refill time of ＞ 4 seconds.His degree of dehydration isIn summary the total volume of fluid the patient need isWhich kind of fliud should be given to the patient first: