The state of the book is:

$\backslash$table$[[,$Trader,Time,Price,Quantity,Display$],[,$Elin,$9$:$45,10\mathrm{.}20,800,$Y$],[,$Sophia,$9$:$40,10\mathrm{.}09,500,$Y$],[,$Will,$9$:$38,10\mathrm{.}09,100,$Y$],[,$Adam,$9$:$43,10\mathrm{.}05,300,$N$],[$Sell$,$Lucas,$9$:$42,10\mathrm{.}05,200,$Y$],[,,,,,],[$Buy$,$Ellen,$9$:$42,10\mathrm{.}03,400,$N$],[,$Ada,$9$:$41,10\mathrm{.}02,300,$Y$],[,$David,$9$:$43,9\mathrm{.}99,200,$Y$],[,$Renee,$9$:$44,9\mathrm{.}99,300,$N$],[,$Max,$9$:$46,9\mathrm{.}80,1000,$Y$]]$

Suppose at $9$:$46,$ Avery submits an order, $"$ Sell $600,$ limit $10\mathrm{.}00."$ Then

A$.$ Avery sells $400$ to Ellen at $10\mathrm{.}03$; Avery sells $200$ to Ada at $10\mathrm{.}02$; Now, the best bid and offer in the market are: $9\mathrm{.}99$ bid for $200($David$),200$ offered at $10\mathrm{.}05($Lucas$).$

B$.$ Avery sells $400$ to Ellen at $10\mathrm{.}03$; Avery sells $200$ to Ada at $10\mathrm{.}02$ ; Now, the best bid and offer in the market are: $10\mathrm{.}02$ bid for $100($Ada$),200$ offered at $10\mathrm{.}05($Lucas$).$

C$.$ Avery sells $400$ to Ellen at $10\mathrm{.}03$; Avery sells $200$ to Ada at $10\mathrm{.}02$; Now, the best bid and offer in the market are: $10\mathrm{.}02$ bid for $300($Ada$),200$ offered at $10\mathrm{.}05($Lucas$).$

D$.$ Avery sells $300$ to Ada at $10\mathrm{.}02$ ; Now, the best bid and offer in the market are: $9\mathrm{.}99$ bid for $200($David$),200$ offered at $10\mathrm{.}05($Lucas$).$