Instructions: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Input: Passage: Julie Cullen is a young divorced parent, on her own for the past four years since her husband abandoned her and their daughter, Ellen, only a year old at the time.  At work, Julie, who is white, meets Frank Richards, who is black, and the two strike up a friendship that blossoms into a romance.  Their relationship is strained by the racial prejudices of many around them, including Frank's parents, William and Martha, who oppose the pairing.  But ultimately Frank and Julie decide to persevere through such difficulties.  They marry, and Julie and Ellen move in with Frank and his parents.  Ellen's arrival immediately softens Martha's heart, but William remains cool toward Julie, steadfast in his belief that Frank and Julie's marriage is a foolish endeavor.  His attitude changes only when Frank and Julie have a son together.  When William first holds his new grandson, he loses any remaining animosity and the household becomes a happy one for all.
Eventually, Julie's ex-husband, Joe, returns, seeking to establish a visitation relationship with Ellen.  However, when he finds that Julie's and Ellen's new family is black, he finds this unacceptable and petitions the court for legal custody of Ellen.  Frank's lawyer tells him that Joe is likely to win.  Agreeing with the lawyer's analysis, William advises Frank to take Julie and the children and flee the state.  Frank, however, decides to stay and fight the case in court.  When Julie appeals to Joe directly, it only angers him, and he even briefly attempts to force himself on Julie physically.  When Frank learns what has happened, he is intensely frustrated by his inability to defend his wife by directly confronting Joe, since he knows that if he does, that will be the end of whatever small chance he and Julie have of winning the custody case.
Output:
Who is Ellen's father?