DB Engine :: Possible Ways To Execute A Query Joining Three Tables

I am learning the Optimizer from the book "Querying Microsoft SQL Server 2012" for certificate exam 70-461. I really cannot understand how it explains the number of possible ways to execute a query joining three tables. the pseudo-query is:

SELECT A.col5, SUM(C.col6) AS col6sum
FROM TableA AS A
INNER JOIN TableB AS B
ON A.col1 = B.col1
INNER JOIN TableC AS C
ON B.col2 = c.col2
WHERE A.col3 = constant 1
AND B.col4 = constant2
GROUP BY A.col5;

The book says:"Start with the FROM part. Which tables should SQL Server join first, TableA and TableB or TableB and TableC? And in each join, which of the two tables joined should be the left and which one the right table? The number of all possibilities is six, if the two joins are evaluated linearly, one after another."

Q1: How could it be six possibilities? From my understanding, lets say, if the SQL Server has to join A and B first, and then join C, in this case I can think of 4 possibilities, which are:

1. When A Join B, Left: A, Right: B.
    When Join C, Left: result of A join B, Right: C

2. When A Join B, nbsp;  
When Join C, nbsp;When A Join B, nbsp;  
When Join C, nbsp;When A Join B, nbsp;   
When Join C, "line-height:13.5px;">

Q2: The section following the previous question says there are 4 different types of join.."This already gives four options for each join. So far, there are 6 x 4 = 24 different options for only the FROM part of this query."

How can it be 6 x 4? My understanding is 4 is only for 1 join, but in our case, there are 2 joins, so it should be 6 x 4 x 4.