In a certain state, a survey of 434 workers showed that 26% belonged to a union. Find the 91% confidence interval of true proportion of workers who belong to a union.
a. (0.3118, 0.3882)
b. (1578, .3511)
c. (0.1983, 0.2798)
d. (0.2243, 0.2957)
e. (0.24, 0.45)