$2.$ Mountain Stream Trout, Inc., agreed to buy market size trout from trout grower Lake Farms, LLC$.$ Their five$-$year contract did not define market size. At the time, in the trade market size referred to fish of one$-$pound live weight. After three years, Mountain Stream began taking fewer, smaller deliveries of larger fish, claiming that market size varied according to whatever its customers demanded. Lake Farms filed a suit for breach of contract.Is outside evidence admissible to explain market size? Yes. Under the UCC, in interpreting a commercial agreement, a court will assume that the usage ofbetween the parties was considered whenthe contract was formed. Also, the conduct that occurs under an agreement, the course of$-$ isthe best indication of what the parties meant. Here, theusage at the time of the contract indi$-$cated that market size referred to fish of one$-$pound live weight. This was the standard for the course ofbetween the parties over the first threeyears of the contract.