Please answer the following question: Who gives Susan's brother a rock?  Answer the above question based on the context below:  LA siblings Ted and Susan Johnson join their parents in Kenya where their father, Earl, works at a NASA tracking station, and their mother, Jean, works at a clinic. Ted's dreams of roughing it on the savannah are squashed when Jean leads him into a house that looks like it belongs in Pasadena, California. Although Jean forbids her children to explore, Ted and Susan sneak out to a nearby watering hole to meet with a Masai tribal boy named Morogo. Morogo shows the siblings the wildlife of Kenya and they show him how to play video games. One day, Jean comes home to discover Morogo in her home. Ted and Susan plead with their parents to let Morogo be their guide and the parents reluctantly give in. One day, Ted kicks a soccer ball over a barrier and it lands against a sleeping rhino. Morogo sneaks up on the animal, retrieves the ball, and places a small stone on the rhino's side. He then gives Ted another stone, daring him to do the same. The rhino awakens as Ted nears, causing him to flee. A laughing Morogo tells him that a person must approach a rhino downwind or it will smell him. Kipoin, Morogo's father, is displeased his son is keeping company with Americans, because they are "cattle eaters" and is even more disgusted to learn they eat fish. One day, the trio comes across a cheetah cub whose mother has been killed by a poacher. Susan insists they take the cub home and talk their parents into letting them raise it. The cub, Duma, becomes the household pet, playing ball, wrestling, and riding in the family car. Ted trains her to come when he blows a whistle. A few months later, however, the Johnson family are convinced their children, who are about to return to the U.S., to free Duma and train her to hunt according to the advice of an Australian game warden named Larry.
Answer:
Morogo