• This is an update Text book for beginning graduate students in Mathematics, Probability and Statistics, Engineering, Computer Sciences, Mathematical Economics • It distinguishes from all existing texts on the subject from its pedagogical spirit, namely, motivations before mathematics; mathematics tools are only introduced when needed and motivated • All theoretical results are proved in a friendly fashion • Teaching the students not noly the concepts and possible applications, but also guiding the students with proof techniques • This series will help students to learn with full understanding and appreciation of the subject • It will provide interested students with solid background for reserarch