researcher wanted to find the best viewing distance for watching a TV screen.He recruited the following number of participantsand asked them to evaluate their satisfaction of the viewing distance.Then,he conducted an ANOVA to see if there is any significant mean differences.Here are the number of participants by each group:

Group1(4feet)-5people

Group 2(7feet)- 5 people

Group 3(10feet) - 6 people

Group 4 (13 feet) - 5 people

Group 5 (16 feet) - 4 people

Given the numbers as presented above, what is thedegrees of freedom for within groupsfor this analysis?

a.4

b.20

c.25

d.21