The employee's primary employment in agriculture during the exempt week is also required to be by “such farmer.” The phrase “such farmer” refers to the particular farmer by whom the employee is employed in agriculture and who engages in the livestock auction operations as an adjunct to his raising of livestock. Even if an employee may spend more than half of his work time in a workweek in agriculture, he would not be exempt if such employment in agriculture were engaged in for various persons so that less than the primary portion of his workweek was performed in his employment in agriculture by such farmer. For example, an employee may work a 60-hour week and be employed in agriculture for 50 of those hours, of which 20 hours are worked in his employment by the farmer who is engaged in the livestock auction operations, the other 30 being performed for a neighboring farmer. Although this employee was primarily employed in agriculture during the workweek he is not exempt. His primary employment in agriculture was not by the farmer described in section 13(b)(13) as required.