a) Identify and briefly explain the four different types of NOSQL data stores, giving examples of typical usage and available products. b) You are creating a web- based interfere to allow for the ad- hoc querying and reporting on a large (and growing collection of various types of customer invoice, where the main key is an invoice ID (but the customers and products purchased are also of high interest). with references to Key-value, document and graph store NoSQL system, evaluate each as a potential persistence layer for the application. c) Explain and describe the CAP theorem. Illustrate a proof. Note: please fast and send me references as well