Please help me understanding the below concepts with an explanation

Question : A brandmanager is concerned about her brand's share distribution throughout the country. In a survey in which the country was divided into 4 geographic regions, a random sampling of 100 consumers in each region was surveyed with the following results:

	Region 1	Region 2	Region 3	Region 4	Total
Purchase the brand	40	55	45	50	190
Do not purchase	60	45	55	50	210
Total	100	100	100	100	400

a) Develop a table of observed and expected frequencies for this problem.

b) Calculate the sample ² (chi-square) value.

c) State the null and alternate hypotheses.

d) Using the 0.05 level of significance, should the null hypothesis be rejected?