Option 1:
1:28 PM
- Ellen left at 1:00 PM
- It took her 15 minutes to walk to the store, so she arrived at 1:15 PM
- She spent 13 minutes in the store, so she left at 1:28 PM
- It takes her 15 minutes to walk back home, so she arrived back at home at 1:43 PM
Option 2:
1:58 PM
- Ellen left at 1:00 PM
- It took her 15 minutes to walk to the store, so she arrived at 1:15 PM
- She spent 13 minutes in the store, so she left at 1:28 PM
- It takes her 15 minutes to walk back home, so she arrived back at home at 1:43 PM
- However, she also spent 15 minutes talking to her neighbor on the way back, so she didn't arrive home until 1:58 PM.