confused by delayed cost and realized profit/loss in Volume 5

The practice problem of 11 of Volume 3 Suppose 1,000 shares of Acme co. Stock are ordered to be bought on Monday with a benchmark price of $10. On Monday, 600 shares are purchased at $10.02 per share. Commission and fees are $20. On Tuesday, the benchmark price has fallen to $9.9 per share. On Tuesday, 100 more shares for Acme close on Tuesday at $10.01 per share. The remaining shares are not purchased, and the order is canceled on Wednesday just as the market closes at $10.05 per share B. Calculate the components of the implementation shortfall for this trade The answer of problem 11: Delay cost Monday: 600/1000 *[($10-$10)/$10] =0% Tuesday: 100/1000 *[($9.9-$10)/$10] =-0.01% Realized profit and loss cost Monday: 600/1000 *[($10.02-$10)/$10] =0.12% Tuesday: 100/1000 *[($10.08-$9.99)/$9.99 =-0.09% Missed trade opportunity cost 300/1000 *[($10.05-$10)/$10 =0.15% My questions are below: 1) Which benchmark should I use in calculating realized gain/loss and delayed costs? 2) No close prices for Monday and Tuesday? Just benchmark for Monday and Tuesday available ? Any one can clear the concepts of realized gain/loss and delayed costs based on the practice above? the followings are definitions of realized gain/loss and delayed costs based on Schweser note and CFAIII book Schweser note the formula of realized gain/loss = Execution price -previous day close/Benchmark * shares purchased/share ordered the formula of delayed costs= previous day closing price - benchmark close/benchmark price * shares purchased/shares ordered Volume 5 of CFAIII book “Delay cost, reflecting the change in price (close-to-close price movement) over the day an order is placed when the order is not executed that day”. compared to the definition of Schweser, no benchmark is mentioned. Why? Thanks!