Paul the postal carrier had an unusual week involving the ten properties along Park Place. Each day of the week Monday through Saturday he delivered mail to four houses. Eight of the houses received mail on three days and two houses got no mail.

The houses along Park Place are numbered 1 to 10. The sum of the house numbers Paul delivered for each day of the week were:
- Monday: 12
- Tuesday: 18
- Wednesday: 23
- Thursday: 32
- Friday: 25
- Saturday: 19

Which two houses did not receive mail?