Diego owns vacant property. Walmart offers to buy Diego$$s property for $$500,000$ with plans to build a new store there if feasible. First, Walmart must conduct a traffic study to determine if the site is feasible. Walmart and Diego agree that Walmart will pay $$35,000$ in exchange for which Diego agrees to hold the offer open for Walmart $($i$.$e$.,$ Diego will not enter into a contract with another party$)$ for $60$ days. What kind of a contract have they formed?

Group of answer choices

letter agreement

firm contract

option contract

anticipatory contract