In a study comparing response rates between treated and non-treated subjects, 30% of subjects are observed to have both responded and been treated. If we also know that a randomization ratio of 1:1 was used (e. g. 1 out of every 2 subjects were treated), then we can calculate that the probability of response among treated subjects is. a. Indeterminateb. 0.9c. 0.594d. 0.6