Walling Retail sent the following order to Pospisil Supply "send us $100$ blue hammers at $$4\mathrm{.}00$ each." Pospisil Supply responded that they "would ship the hammers later that day." To Pospisil's dismay that afternoon they found that they only had $99$ blue hammers in stock so they shipped $99$ blue hammers and $1$ red hammer. They sent the $99$ blue hammers and $1$ red hammer and did not indicate that they were doing so only as an accommodation.

This is not a breach because they were trying to accomodate Walling Retail.

This is a counteroffer since this was a unilateral offer which can only be accepted by shipping.

This is a breach because they did not ship conforming goods.

This is not a breach as they substantially complied with the contract.