Answer:
1) 2.71%
2) $38.32
Explanation:
Opening balance = $1220
Balance after 10 days (after expense) = $1690
Balance after 10 days(after payment) = $1340
APR = 33%
1) Periodic interest rate = APR ×

= 33%× 30/365
= 2.71%
2) Interest charged for first 10 days =

= $11.02
Interst charged for the next 10 days =

= $15.2
Interest charged for the next 10 days =

= $12.10
Total interest for 30 days = 11.02+15.2+12.10
= $38.32