You are required to integrate prescriptive analytics into a report for a logistics company aiming to optimize their delivery routes. The dataset includes 'RouteID', 'Distance', 'Time', 'VehicleType', and 'Cost'. Describe how you would use optimization models in Microsoft Fabric to suggest the optimal routes for each vehicle type, considering factors like distance, time, and cost. Include the type of optimization model you would use and the data preprocessing steps necessary.