The county treasurer, following board approval of the sale and reapportionment shall complete the sale of the subdivided parcel upon payment by the purchaser of the total of the following sums, less the amount of the partial payment made by him:
(a)
The sum of delinquencies, penalties and interest apportioned and charged to the subdivided parcel.
(b)
Interest on the amount for which the parcel was sold, as apportioned to the parcel, at the rate of 7 percent per year compounded annually from the date set forth in the reapportionment list to which interest was computed, to the date of the sale.
(c)
The cost of making the reapportionment as charged to the parcel.