there must be an audience that enjoys the friday series , but 
(ROOT (S (S (NP (EX there)) (VP (MD must) (VP (VB be) (NP (NP (DT an) (NN audience)) (SBAR (WHNP (WDT that)) (S (VP (VBZ enjoys) (NP (DT the) (NNP friday) (NN series))))))))) (, ,) (CC but)))
(ROOT (S (S (NP (EX )) (VP (MD ) (VP (VB ) (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (NP (DT ) (NNP ) (NN ))))))))) (, ) (CC )))