$3.$ Acme Industries has offered to sell a piece of equipment to ABC Inc. for $$250,000$ and has promised to keep the offer open to be accepted for two weeks. What is Acme's legal position in this case?

$($a$)$ The promise to keep the offer open for acceptance is not valid, as it is against public policy

$($b$)$ Acme can revoke the offer any time after it is made

$($c$)$ Acme must legally keep the offer open for acceptance for the two weeks

$($d$)$ The offer can only be revoked if ABC agrees to$$the$$revocation