Define request edge and assignment edge.
Answer: A directed edge from process Pi to resource type Rj is denoted by Pi->j; it signifies that process Pi requested an instance of resource type Rj and is currently waiting for that resource. A directed edge from resource type Rj to process Pi is denoted by Rj->Pi, it signifies that an instance of resource type has been allocated to a process Pi. A directed edge Pi->Rj is called a request edge. A directed edge R->Pi is called as an assignment edge.