Creating Synthetic Cash different, position, question, selling, convert

invic

Hello - I am somewhat confused by a problem in Schweser 2012 Practice Test Book 1; Test 2; Afternoon question 37 (page 133). This question asks to convert a $3 billion position into synthetic cash by selling futures contracts. As I was working on this question, it dawned on my that I have two different ways to create synthetic cash in my head.
#1) [(Target Beta - Portfolio Beta) / Futures Beta ] * ( V / (Pf)*multiplier )
       (using a Target of 0 or .25)
#2) - V * (1 + RF)^T / (Pf)*multiplier
The answer to the question uses the second formula. However, I used the first when I saw the question. Of course my answer was there as a wrong answer. The answer key doesn’t provide any information as to why. If someone can please let me know when to use which formula, I would be most grateful
Thank you very much.