LongDrive sells a specialized golf club that has core plugs to shift weight in the club head and produce different ball flights. LongDrive sells the golf club and replacement core plugs separately, and no other company sells either item. Customers can use the golf club without the replacement core plugs, but the replacement core plugs are not usable without the golf club. LongDrive sells the golf club and four replacement core plugs to a customer. The golf club is shipped on April 1, 2017, and the replacement plugs are shipped on May 1, 2017. How many performance obligations does LongDrive have with respect to this sale?