Explanation
Using an Enterprise Service Bus (ESB) to determine which shipping service to use, and transform requests to the necessary format is a good solution because it can provide routing, transformation, mediation, and orchestration capabilities for integrating different services. An ESB can also abstract the complexity and heterogeneity of the services from the client application, which simplifies the integration. Using Outbound Messaging to request costs and delivery times from Shipper delivery services with automated error retry is not a good solution because Outbound Messaging is a Salesforce-specific feature that uses SOAP web services, which may not be compatible with all shipping services. Using APEX REST Service to implement routing logic to the various shipping service is also not a good solution because it can introduce performance and scalability issues, as well as increase the maintenance cost and complexity of the code. Using Enterprise Service Bus user interface to collect shipper-specific form data is not a valid option because an ESB does not have a user interface component. Reference: Salesforce Integration Architecture Designer Resource Guide, page 16-17