Paloma owed $400 on a credit card at the end of the March billing cycle.
She made a purchase of $600 with 20 days left in the April cycle.
She then made a payment of $300 with 10 days left in the April cycle.
The April cycle is 30 days long.
The credit card's APR is 21%.
Using the adjusted balance method, how much interest is Paloma charged for
the April cycle?
A. $22.44
B. $1.72
C. $12.08
D. $84.00