Help me answer this question so I can compare my answer

Question $3)$ A consumer products company relies on direct mail marketing pieces as a major component of its advertising campaigns. The company has three different designs for a new brochure and wants to evaluate their effectiveness, as there are substantial differences in costs between the three designs. The company decides to test the three designs by mailing $5000$ samples of each to potential customers in four different regions of the country. The company acknowledges that there might be differences across different regions in the customer base, they considered to use a Randomize complete Block DEsign. The number of responses to each mailing is as follows.

a$)$ What is the main factor and how many levels does it have?

b$)$ What is the factor that is considered as block?

c$)$ Based on the following output, what can you cay about the effect of design on number of responses they receive at alpha $\backslash (=0\mathrm{.}05\backslash )?$

Analysis of Variance