· 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 only 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 research