Use TABLE ll below and the attached map A for Nigeria to answer the questions that follow TABLE II: Volume of Rail Passenger Traffic Generated by Five Nigerian cities, 1973 

CITIES	RAIL PASSENGER TRAFFIC
IBADAN	5,000,000
ENUGU	3,000,000
MAIDUGURI	2,500,000
POTR HARCOURT	1,500,000
MINNA	1,000,000

(a) Represent the statistics with proportional circle,

(b) Outline two advantages of representing data wits proportional symbols