sparked by two actresses in their 50s working at the peak of their powers . 
(ROOT (S (VP (VBN sparked) (PP (IN by) (NP (NP (NP (CD two) (NNS actresses)) (PP (IN in) (NP (PRP$ their) (NNS 50s)))) (VP (VBG working) (PP (IN at) (NP (NP (DT the) (NN peak)) (PP (IN of) (NP (PRP$ their) (NNS powers))))))))) (. .)))
(ROOT (S (VP (VBN ) (PP (IN ) (NP (NP (NP (CD ) (NNS )) (PP (IN ) (NP (PRP$ ) (NNS )))) (VP (VBG ) (PP (IN ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (PRP$ ) (NNS ))))))))) (. )))