Concentrated Positions - Short Against the Box

[Broken Model]

Short against the box, where the investor shorts against a concentrated position he is currently long. The cfai states this:
“Because the long and short positions together constitute a riskless position, the investor will earn a money market rate of return on the $100 million position. The investor has economically transformed the risky ABC Corp. stock position into a riskless asset that will earn a money market rate of return.”
I understand the riskless asset part, but the earning a money market return is confusing me. Where is this return coming from? Is it implied that the proceeds of the short are then invested at the risk free rate?

 

[Influence]

I remember this same question came up when I read this, and my conclusion was similar to yours: it is implied that the proceeds of the short position are invested at the risk free rate.

 

[Godism17]

Because the whole purpose of shorting against the box was a way to manage a concentrated position to reduce risk in his/her total wealth. Reinvesting in risky assets again doesn’t help to eleminate the problem. Cash is safest, riskless and implied.
CFAI has also implided the investor is “prudent” and “rational” lol Keeping 100M in short term T-bills and such is smarter than blowing it on “human weakness” : goregous men, exotic animals, toys, etc. Can’t say I would be that responsible with 100M after running this strategy…hahaha