Lana has a credit card that uses the adjusted balance method. for the first 10 days of one of her 30-day billing cycles, her balance was $2800. she then made a payment of $1200, so her balance decreased to $1600, and it remained that amount for the next 10 days. lana then made a purchase for $500, so her balance for the last 10 days of the billing cycle was $2100. if her credit card's apr is 35%, how much was lana charged in interest for the billing cycle?