VI. Alex died without a will, leaving only an undeveloped and untitled lot in Tagiug City. He is survived by his wife and 4 children. His wife told the children that she is waiving her share in the property, and allowed Bobby, the eldest son who was about to get married, to construct his house on ¼ of the lot, without however obtaining the consent of his siblings. After settlement of Alex's estate and partition among the heirs, it was discovered that Bobby's house was constructed on the portion allocated to his sister, Cathy asked Bobby to demolish his house and vacate the portion alloted to her. In leiu of demolition, Bobby offered to purchase from Cathy the lot portion on which his house was constructed. At that time, the house constructed was valued at P350.000. Can Cathy lawfully ask for demolition of Bobby's house? (3%) Can Bobby legally insist on purchasing the land? (2%)