An endothermic reaction is one that requires energy in the form of heat, which you observe from the outside as the chemical getting cold (like in a cold pack). An exothermic reaction is the opposite, generating heat on its own through the reaction (like in a hot pack).
B A C ( Blood Alcohol Content ) of 0.10 means that there are 0.10 g of alcohol for every dl of blood. 5 L = 50 dl 50 * 0.10 g = 5 g In his blood is circulating 5 grams of alcohol.