This program should return the value $30.$ The key idea is this:

a$)$ Start with an empty environment map to begin with.

b$)$ Execute each statement in the list of statements from beginning to end.

When you execute the statement, do so with the current map and the return value is the next map.

c$)$ Evaluate the return expression on the final map after you have executed all the statements.

Complete the code below. You can use loops and var for now. We will show you how to avoid it later.

Here is how you iterate through each element of a list in scala: