penalty interest rate calculation on lease

Amount Paid 0 Date April 2020 May 2020 June 2020 July 2020 August 2020 Amount Due 3000 3000 3000 3000 3000 0 Overdue 3000 3000 3000 1500 1500 12,000 Mos 1.00 1.00 1.00 1.00 1.00 0 1500 1500 Johnson Inc. was late on several lease payment and according to the lease contract, Johnson Inc. is given 10 days grace period after due date to pay without subjecting to the penalty interest. The due date for the lease is the 1st of every month. Johnson Inc did not pay the lease for April through June and only half for July and August as shown in the table above. The penalty interest rate is 6% and Johnson Inc did pay off the overdue amount ($12,000) on August 6 With this information, calculate the total amount Johnson Inc owed in least payment