Which research method involves manipulating a variable in order to determine how it affects another variable (in a cause and effect relationships)?

Consider the following limit order book for a share of stock. the last trade in the stock occurred at a price of $50. limit buy orders limit sell orders price shares price shares $49.75 500 $49.80 100 49.70 900 49.85 100 49.65 700 49.90 300 49.60 400 49.95 100 48.65 600 a. if a market buy order for 100 shares comes in, at what price will it be filled? (round your answer to 2 decimal places.) b. at what price would the next market buy order be filled? (round your answer to 2 decimal places.) c. if you were a security dealer, would you want to increase or decrease your inventory of this stock? increase decrease