The expected answers were:
(a) Impedance of an a.c. circuit is the opposition of a circuit element or a

            combination of circuit elements to current flow.
                                              
(b)(i)    Impedance, Z = √R2 + (XL-XC)2          
                                                                                                 
                                             = √32 + (8-4)2
                                               =  5Ω
         
              (ii)     V = IZ
                        Current, I = V    =  250  =   50A
                                             Z          5

             (iii)     Power factor = IR  =  IR  =  R
                                                 V       IZ       Z 
                                             = 3/5  =  0.6

This question was on alternating current circuit theory. It was popular among the candidates.  Part (a) was well-answered. 

Most candidates answered part (b) very well too.  The processes involved in the calculation were well-understood.