to do justice to either effort in three hours of screen time 
(ROOT (S (VP (TO to) (VP (VB do) (NP (NN justice)) (PP (IN to) (NP (CC either) (NN effort))) (PP (IN in) (NP (NP (CD three) (NNS hours)) (PP (IN of) (NP (NN screen) (NN time)))))))))
(ROOT (S (VP (TO ) (VP (VB ) (NP (NN )) (PP (IN ) (NP (CC ) (NN ))) (PP (IN ) (NP (NP (CD ) (NNS )) (PP (IN ) (NP (NN ) (NN )))))))))