Final answer:
For items with significant monetary value, Priority Mail is the recommended class, with the option to add Certified Mail for additional security. In the mailroom scenario, kilograms or grams would be the suitable metric units for weighing packages.
Step-by-step explanation:
When sending an item that has significant monetary value, the class of mail that should be used is Priority Mail. This service offers more security through tracking and insurance options than other classes like First-Class Mail, Media Mail, or Standard Post. However, an additional service called Certified Mail can be added to the Priority Mail to provide proof of mailing and delivery, which enhances the security when sending valuable items.
Jesse, who works in the mailroom, is responsible for ensuring correct postage based on size and weight of the mail. Since he is given a box with 10 books and some documents, the appropriate metric unit of measurement for weighing the package is kilograms (kg) or grams (g), depending on the total weight of the package.