Peak Roofing sent Jensen Builders an invoice dated July 12 for $5400 with terms 3/10, 1

Question:

Peak Roofing sent Jensen Builders an invoice dated July 12 for $5400 with terms 3/10, 1 ½ /20, n/45. Jensen made a payment of $2000 on July 20, and a second payment on 2 August 1 that reduced the balance owed to $1000. What was the size of the second payment?