No Loops solution using SQL

Recently came across a problem posed here. Basically, it is a test for a programmer to see if she can come up with a solution using a set-based, non-procedural approach to the problem. Two set-based solutions are already presented at the link. Here I present another solution.

What is the problem?

For the sake of completeness, here is a copy of text of the problem, verbatim, from the above link.

You have a table of trading days (with no gaps) and close prices for a stock.

CREATE TABLE stock (
      trading_date DATE UNIQUE,
      price FLOAT
 );

Find the highest and lowest profits (or losses) you could have made if you bought the stock at one close price and sold it at another close price, i.e. a total of exactly two transactions.

You cannot sell a stock before it has been purchased. Your solution can allow buying and selling on the same trading_date (i.e. profit or loss of $0 is always, by definition, an available option); however, for some bonus points, you may write a more general solution for this problem that requires you to hold the stock for at least N days.

The problem also provides some synthetic data which I am copying here again for reproducibility purposes.

INSERT INTO stock VALUES
('2015-06-01', 41),
('2015-06-02', 43),
('2015-06-03', 47),
('2015-06-04', 42),
('2015-06-05', 45),
('2015-06-08', 39),
('2015-06-09', 38),
('2015-06-10', 41);

Given this dataset, the biggest profit you can make is $6, and the smallest profit is -$9 (i.e. a loss of $9).

My no loop solution

As stated before, the source link provides you with 2 solutions. Here is my solution to the problem:

;with CTE1(price, max_following_price, min_following_price) as
(
 select price
  , max(price) over(order by trading_date asc rows BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
  , min(price) over(order by trading_date asc rows BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
 from stock
),
CTE2 as
(
select max_following_price-price as greatest_potential_profit
 , min_following_price - price as smallest_potential_profit
from CTE1 
)
select MAX(greatest_potential_profit) as highest_profit
 , MIN(smallest_potential_profit) as lowest_profit
from CTE2