The radius of a circular oil slick expands at a rate of 2 m/min.

(a) how fast is the area of the oil slick increasing when the radius is 25 m
(b) if the radius is 0 at time , how fast is the area increasing after 4 mins

Agroup of student volunteers participates in a study designed to assess several behavioral interventions for improving output in a repetitive task. prior to the beginning of the study, all volunteers unknowingly observed, and their output is measured. at the beginning of the study, prior to any intervention, the volunteers perform the same task under the observation of a study administrator, and their overall output increases. which of the following terms describes this phenomenon? a. simpson's paradox b. hawthorne effect are d. novelty effect d. pygmalion effect e. observer-expectancy effect