i tried this but i think my method os wrong, appreciate any help!

The table below shows the limit-order book of Stock XYZ when the market opens this morning. Buy Orders Price Sell Orders Shares Price Shares $10 150 $12 300 $9 100 $12.5 200 $8.5 250 $13 100 $8 100 $13.5 100 a. Suppose that Frank submits a limit sell order of 100 shares with price of 10.5, will his order be executed based on this limit order book? b. After Frank submits his order, Alice also comes to the market. Alice submits a market buy order of 500 shares. What is the average price per share that Alice pays? Note that Frank's order might have changed the original limit order book.