Forward Price - Zero Coupon Bond Arbitrage - Please explain logic!

Could you please help me understand the logic behind solving this problem below. I would much appreciate it!

Term Yrs / Spot Rates

R (2) - 1.5%

R (4) - 1.9%

R (6) - 3.0%

R (8) - 4.0%

You are exploring a 4yr forward contract in which the underlying is a 2yr zero-coupon bond, which is trading at $90.09 per 100 of par. Using the forward model, is there arbitrage.

A. does not exist

b. profit of $0.56

c. profit of $2.80

This makes no sense: the bond matures 2 years before the forward expires.

Please recheck your numbers.

This is exactly how the question is layed out!

a 4yr forward contract in which the underlying is a two year zero coupon bond. This means find F(4,2).

So, if I understand this correctly, when the forward expires in 4 years, you can buy or sell a 2-year zero at 90.09.

Weird way of presenting it.

In any case, you need to calculate the 2-year forward rate starting 4 years from today (implied by the current spot rates) and compare that to the 2-year rate implied by the price on the zero.

The former is calculated as:

(1 + 2f4)² = (1 + s6)^6 / (1 + s4)^4

(1 + 2f4)² = (1 + 3%)^6 / (1 + 1.9%)^4

(1 + 2f4)² = 1.1075

1 + 2f4 = 1.0524

2f4 = 5.2358%

If you discount the zero at that rate you get:

100 / (1 + 2f4)² = 100 / 1.1075 = $90.30

So it appears that there’s an arbitrage profit of $0.21, which, alas, isn’t listed.

What’d the official answer say?

Correct answer is B = $0.56

This is how they get to it.

Find the price of a F(4,2) = wait 4 years and enter into a 2 year loan.

Calculated Forward Price: P(4) = 0.90297

Currently trading at = 0.9009 (arbitrage exists!!!)

Profit: .90297-.9009 = 20bps (WRONG).

They take the Calc forward price P(4) & presen value it: 0.90297 * 0.927477(which is the R(4).

After PV both prices, the get $0.56

Calc Fwd Price (0.90297 * 0.927477) = .83748

Trading (0.9009 * 0.927477) = .843077

.843077 - .83748 = 0.005597 *100 = $0.56

It appears that the author cannot multiply correctly.