APE Network is devoted to transform Tanzania’s education through publishing exemplary learning facilities which will simplify understanding and make it more interesting for students. Our aim is to facilitate smooth, efficient and effective learning that can breed candidates with useful skills and right attitudes to bring development to themselves and their communities. At the level of knowledge and exposure in which Tanzania and the rest of Africa are, it is apparent that we only need an activator to transform the massive potentials in our minds into tools that can improve our lives and bring development. This is what APE Network is, a motivator towards effective acquisition and application of education. The images, figures and examples used in our books are picked from our country or at least our Region (East Africa). With these efforts we hope to increase not just students’ performance, but essentially their perception of knowledge, understanding and creativity in handling everyday problems and joys. APE Network acknowledges the devoted contribution of the following in the preparation of this book: