I would imagine - and note my words, I am not being definitive - that it would be viewed in the same way as 'offer and acceptance' for a contract. The offer stays open until rescinded, which includes replacement by another offer.
Up until that point, your 'offer' is open. Note though that - unlike in contract law - the PM has an obligation to assess the quotation in accordance with the contract as an "impartial administrator". Consequently, due to the extra information supplied, if he or she is aware that it is too low, then he or she should make their own correct assessment.
Up until that point, your 'offer' is open. Note though that - unlike in contract law - the PM has an obligation to assess the quotation in accordance with the contract as an "impartial administrator". Consequently, due to the extra information supplied, if he or she is aware that it is too low, then he or she should make their own correct assessment.