Explanation
A query activity is an automation studio activity that allows querying data from data extensions or data views using SQL statements. A data extension entry source is a journey builder entry source that allows injecting contacts into a journey based on a data extension. Journey activities are actions that occur within a journey, such as sending an email or updating a contact attribute. By using a query activity to filter contacts who have not made a purchase in the last six months from their order data extension, NTO can create a sendable data extension with those contacts and use it as a data extension entry source for their journey. Then, by using journey activities, they can communicate the same message across all channels to those contacts. References:
https://help.salesforce.com/articleView?id=sf.mc_as_sql_query_activity.htm&type=5
https://help.salesforce.com/articleView?id=sf.mc_jb_data_extension_entry_source.htm&type=5
https://help.salesforce.com/articleView?id=sf.mc_jb_journey_activities.htm&type=5

Explanation
To separate subscriber opt-outs of the Enterprise and children's brands, Northern Trail Outfitters should select
"Subscribers will be unsubscribed from this business unity only" in Settings for each child business unit. This will allow subscribers to unsubscribe from one brand without affecting their subscription status for another brand. References: https://help.salesforce.com/s/articleView?id=sf.mc_co_business_unit_setup.htm&type=5

To connect relational data into their journey without overloading the entry data, Northern Trail Outfitters should use Data Designer. Data Designer is a tool that allows marketers to create attribute groups that link different data sources in Contact Builder. This way, they can access relational data in decision splits and other journey activities without having to include all the data in the entry source data extension.References:https://help.salesforce.com/s/articleView?id=sf.mc_co_data_designer.htm&type=5

With a Sender Authentication Package (SAP) and dedicated IP address, maintaining a minimum volume (around 250,000 messages/month) is critical to building and maintaining a healthy sender reputation. If the volume drops too low, deliverability could be negatively affected.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - Dedicated IP Warming and Maintenance
# "To maintain a strong sending reputation on a dedicated IP address, customers should send a minimum of
250,000 emails per month."
Source: Salesforce Marketing Cloud Implementation Guide - Sender Authentication Package
# "Dedicated IPs provided with SAP require consistent, high-volume sending for optimal performance."
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