6.2 ADT Firsto: return first element of the queue Lasto return last element of the queue Add (): add element x to the queue Delete(x): delete front element from the queue and put it in x;6.2 ADT First():return first element of the queue; Last():return last element of the queue; Add(x):add element x to the queue; Delete(x):delete front element from the queue and put it in x; }