a) Brazilian ATC, for unknow reason(s) under investigation, forget to include DAKAR ATC when the flight plan was dispatched to all concerned air controls, but DAKAR (GOOO) was rightly inserted in the flight plan delivered by Air France to Brazilian ATC.
a) The FAB states it is a periodic flight plan and that it was sent to DAKAR ATC
b) The FAB also states that there is an agreement between Brazil and Senegal providing that after three minutes from the estimated time for a given a/c to enter the area under DAKAR jurisdiction from the Brazilian one and vice-versa, the control is considered to be transfered to that jurisdiction without any further communication. And as DAKAR ATC didn't seek any information from ATLANTICO long after that estimated time the flight already was, officially, under DAKAR FIR control.