Arbitrage Profit on a Bond Futures Contract Under Carry Arbitrage

Quoted Futures Price 125

Conversion Factor 0.9

Time Remaining to Contract Expiration - 3 months

Accrued Interest over life of contract 0

Underlying Bond:

Quoted Bond Price 112

Accrued Int. since last coupon 0.08

Accrued Int. at Futures expiration 0.20

Based on Exhibit 1 and assuming annual compounding, the arbitrage profit on the bond futures contract is closest to:

Answer is 0.5356.

When I am trying to find arbitrage profit for a bond futures contract under carry arbitrage, why do I have to compare the futures price on the actual bond? Why does it not work when I compare the quoted futures price (generic bond)?