In a survey of 30 consumers of detergents, 5 people said they are loyal to brand A, while another 5 are loyal to brand B. 7 surveyed said they do not use either brands A, B nor C, but use some other detergent not included in the survey. A total of 10 consumers said they prefer brand A, and a total of 11 consumers said they prefer brand C. There were no one who used both brands B and C. Further, almost peculiarly, no one said they used A, B and C simultaneously. Find the number of consumers who:
a. Preferred brands A and B.
b. Preferred brands A and C.
c. Preferred brands A or B.
d. Preferred brands A or C.
Had a problem constructing the venn diagram, because I'm not sure if what I have done is correct. And I got confused at the last part of the problem. --- 0 uses A, B and C? I need help.