This exercise involves defining an interaction between two BPEL4WS processes. (a) Create a business process definition B1 consisting of receive, invoke, and reply activities that are executed in sequence. (b) Sketch the definition of the portTypes and operations that need to be defined on the external WSDL interface of B1, as viewed by its partners. (c) Create a business process definition B2, in which B1 is defined as a partner. Define an appropriate partnerLink between B2 and B1. Define an invoke activity in B2’s logic, which invokes the request–response operation offered by B1’s external WSDL interface. (d) Comment on whether we can describe B2 as being a subprocess of B1.