The Table below shows the volume of air passenger traffic between Lagos and four other cities in Nigeria in 1985. Study the table and use the data in it to answer the questions that follow: 

S/N	Route	No. of passengers
1	Lagos -  Abuja	500,000
2	Lagos - Enugu	200,000
3	Lagos - Port Harcourt	400,000
4	Lagos - sokoto	300,000

(a) Using the attached map of Nigeria - Map B, construct a flow map/chart to represent the data in Table 1.

(b) State two advantages cf representing data with flow maps.