Please answer the following question: Question: Who kills Brenda? If there is no answer, please output "Insufficient information to provide an answer.". Movie title: Frenzy Context: In London, a serial killer is raping women and strangling them with neckties. Most of the film takes place in Covent Garden, which at the time was still the wholesale fruit and vegetable market district. Fairly early in the film, the audience sees that fruit merchant Robert Rusk (Barry Foster) is in fact the murderer. However, circumstantial evidence has already built up around his friend Richard Blaney (Jon Finch). Blaney's ex-wife, Brenda (Barbara Leigh-Hunt), runs a matchmaking service that Rusk used until he was blacklisted for beating up his dates. One day, Rusk shows up at her office and tries to seduce her; when she spurns his advances, he rapes and strangles her in a fit of rage. Suspicion falls on Blaney, who is previously seen threatening his ex-wife in public, as well as being seen leaving her building shortly after her murder. The subsequent murder of Blaney's girlfriend, Barbara "Babs" Milligan (Anna Massey), occurs off-screen: the audience sees her entering Rusk's apartment with him, but the camera then pulls back down the stairs all the way out to the other side of the street. The audience next sees Rusk at night carrying a large sack and lifting it into the back of a lorry among sacks of unsold potatoes bound for Lincolnshire. Rusk soon finds that his distinctive jeweled tie pin (with the initial R) is missing, and realises that Babs must have torn it off as he was murdering her. He climbs into the back of the lorry, but it starts off on its journey north. The killer desperately scrabbles through the sack of potatoes to find the dead woman's hand. Rigor mortis has set in, and he has to break her fingers in order to prise the pin from her grasp. Owing to fake evidence set up by Rusk, Blaney is gaoled while protesting his innocence. Chief Inspector Oxford (Alec McCowen), the detective investigating the murders, reconsiders the previous events and begins to believe that he has arrested the wrong man. He discusses the case with his wife (Vivien Merchant) in several scenes of comic relief...
Answer:
Robert Rusk