Economics HELP

President Obama has not yet decided whether he will approve a new pipeline (the Keystone XL) that would carry newly produced oil from Canada into key distribution sites in the United States.    

(A)             From an economic standpoint, what are the likely costs and benefits

associated with the President’s decision insofar as the actual construction of the pipeline inside the United States is concerned?   (Ignore its subsequent use.)

(B)              Let’s move to the future.  Suppose the pipeline now is in operation.  Now, who bears the expected economic costs and benefits of the operation of this pipeline?  I.e., who benefits and who pays what costs?