cannot be a valid acceptance under § 2-207(1) and, accordingly, no contract was created by the exchange of forms. See Dorton, 453 F.2d at 1168 (“In order to fall within this [§ 2-207(1) ] proviso, it is not enough that an acceptance is expressly conditional on additional or different terms; rather, an acceptance must be expressly conditional on the offer- or’s assent to those terms.”). Christy argues that, if its customer acknowledgment form was not a valid acceptance of PCS’s offer, then the acknowledgment form was converted into a nonbinding counter-offer to which PCS in turn assented through its acceptance of and payment for the goods. See Brief of Appellant at 27-31; see also Construction Aggregates Corp. v. Hewitt-Robins, Inc., 404 F.2d 505 (7th Cir.1968) (Construction Aggregates) (<HOLDING>), cert. denied, 395 U.S. 921, 89 S.Ct. 1774, 23
holding that a valid contract requires acceptance of an offer holding that purported acceptance was a counteroffer when it conditioned settlement upon satisfaction of liens holding that buyers retention and use of boiler was an act inconsistent with sellers ownership and constituted acceptance precluding rejection holding that although sellers acknowledgment was not valid acceptance of buyers offer under  22071 buyers subsequent acceptance of and payment for goods along with buyers objection to a particular term within counteroffer constituted assent to remaining terms of counteroffer holding that purported acceptance was a counteroffer when response required additional act of resolving all liens