A researcher chooses a sample of 100 people to determine the relationship between gender (male/female) and registering to vote. The sample consists of 40 females, of whom 30 are registered voters, and 60 males, of whom 40 are registered voters. If such data were employed for a chi-square test for independence, what is the expected frequency for registered females?
a. 28
b. 12
c. 42
d. 50