Do the paper trading accounts buy and sell off of the bid/ask price or does it only work based on the current price of the stock?

Environment

Language
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C# Visual Studio with a hint of javascript.

Alpaca SDK Version
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Problem

Summary
Trying to figure out if there is an option to get the bid/ask price so i that i can correctly calculate buys and sells as if it were doing live trades.

Paper or Live Tradng?
Paper Trading

Example Code
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