To calculate the estimated ship date for an Order, the best method is to use a Max Roll-Up Summary field on the Latest availability date fields. A Roll-Up Summary field calculates values from related records, such as the sum, minimum, maximum, or count of a field1. By using a Max Roll-Up Summary field on the Latest availability date fields, the Order record can display the latest date among all the Line Items, which is the earliest date that the Order can be shipped.
The other options are not correct because:
* A. Use a CEILING formula on each of the Latest availability date fields. This option is not valid, because a CEILING formula rounds a number up to the nearest integer2. This does not help to calculate the estimated ship date for an Order, as it does not compare the dates of the Line Items or display the result on the Order record.
* B. Use a DAYS formula on each of the availability date fields and a COUNT Roll-Up Summary field on the Order. This option is not valid, because a DAYS formula returns the number of days between two dates2. This does not help to calculate the estimated ship date for an Order, as it does not account for the latest date among the Line Items or display the result on the Order record. A COUNT Roll-Up Summary field only counts the number of related records, not the values of a field1.
* C. Use a LATEST formula on each of the latest availability date fields. This option is not valid, because there is no such formula function as LATEST in Salesforce2. Even if there was, it would not help to calculate the estimated ship date for an Order, as it would not display the result on the Order record.
References:
* : Roll-Up Summary Fields
* : Formula Operators and Functions