To create a constant whose value cannot be changed, the final keyword must be used. A final variable can only be assigned a value once, either in its declaration or within a constructor. Using the static keyword makes the variable associated with the class itself, rather than with a specific instance of the class, which is the standard convention for defining constants. Therefore, static final is the correct and most precise declaration to ensure the DELIVERYMULTIPLIER value remains constant throughout the application's execution and is accessible at the class level.

1. Apex Developer Guide

"Final Variables": "Use the final keyword to declare a constant. A final variable can only be assigned a value once

either in the declaration itself

or in an init method or constructor." This directly supports the use of final to meet the requirement that the value should not change.

2. Apex Developer Guide

"Static and Instance Methods

Variables

and Initialization Code": "Static variables are associated with a class... All instances of the same class share a single copy of the static variables." This supports using static for a value that should be singular and class-wide

which is characteristic of a constant.

3. Apex Developer Guide

"Variable Declaration": This section outlines the syntax for declaring variables

showing that static and final are access modifiers that precede the data type

confirming the structure static final decimal ....