This question runs in a pre-configured Salesforce environment - no personal connection required.

Transfer all Contacts from a source Account to a target Account by updating the AccountId field. Return the number of Contacts that were successfully transferred.

Return 0 if the source Account has no Contacts. Return null if either the sourceAccountId or targetAccountId is null.

Examples:

Input: sourceAccountId = '001XXXXXXXXXX', targetAccountId = '001YYYYYYYYYY' Output: 5 Explanation: The source Account had 5 Contacts, all were transferred to the target Account Input: sourceAccountId = '001XXXXXXXXXX', targetAccountId = '001YYYYYYYYYY' Output: 0 Explanation: The source Account has no Contacts, so 0 Contacts were transferred Input: sourceAccountId = null, targetAccountId = '001YYYYYYYYYY' Output: null Explanation: Source Account ID is null, return null
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