The Process of Decision Making in Chess Volume 2: Practice positions and solutions. Position 9.4

Solve for black:

Diagram 9.4- white’s isolated f4 pawn is on an open file, which makes it easy for black to attack it, thus putting white on the defensive with the passive f1 rook.

Challenge: can you think of a plan that takes advantage of this weakness to create progress for black?

Where do I find the answers for previous positions which are all very interesting? Thankyou

....B-h3.  R-f2 g5. 

I think these answers assume that Whit'e response to Bh3 will be Re1. I can't see how that's forced.

Sorry. I should have been clearer.  Does Rd2 provide a problem?

..........R f7

Rd2    R(d8)- f8

R(2) to F2    Bh3  I think wins pawn

How about:

.........................Bg4

R(d1) e1      RxR

RxR              Rxf4

Gains the weak pawn.