Some of you have raised a question about the correct translation of

	"It is necessary to wash the boss's car to get promoted"

into "if-then" form (this was a HW#1 problem from p. 18, #18a).

Remember:  "P is a necessary condition of (or "for") Q" means:
	
	If Q, then P.

So, the correct translation is:

   "If you are to get promoted, then you (must) wash the boss's car."

Let's think about it:  The original sentence says that to get promoted,
there's something you have to do--something that is necessary--namely,
wash the boss's car.

Let's consider a truth table:

Let G = you get promoted
Let W = you wash the boss's car.

G	W	(G -> W)	(W -> G)
------------------------------------------------------------------------
T	T	   T		   T
T	F	   F		   T
F	T	   T		   F	
F	F	   T		   T

Suppose you get promoted, and you tell your friend about it.
Your friend, knowing that it's necessary to wash the boss's car in order
to get promoted, can infer that you must have washed the boss's car:

If G, then W.

Suppose you wash the boss's car, and you tell your friend abou it.
Can your friend, knowing that it's necessary to wash the boss's car in
order to get promoted, infer that you got promoted?  No, because maybe
to get promoted you also have to be a good employee.

Washing the car is only a necessary condition for getting promoted,
not a sufficient one.

So:	(G -> W) is the correct translation