In a real estate transaction, if a buyer counters a counteroffer:

$($a$)$ another counteroffer would be prepared, signed, and properly delivered to the seller for consideration.

$($b$)$ the buyer's agent has the option to terminate the contract.

$($c$)$ the entire contract is rejected and negotiations are terminated.

$($d$)$ the original contract would be amended, signed, and properly delivered to the seller for consideration.