(a) Define the following terms:
(i) optimum population;
(ii) over-population;
(iii) population density 

(b) The total population of country Q in the year 1998 was 4 million. If the land area of country Q is 400,000 km2, calculate the population density of country Q

(c) Highlight four disadvantages of the population density calculated in (b) above on the economy of country