# Episode 42 answer check

Source: `order-rows-practice.csv`. Column B is Quantity; column C is Unit price. Add `Line total` to D1 and use only one formula in D2:

```text
=ARRAYFORMULA(IF(B2:B="","",B2:B*C2:C))
```

| Row | Arithmetic | Expected D |
| --- | --- | ---: |
| 2 | 2 × 12 | 24 |
| 3 | 3 × 7 | 21 |
| 4 | 1 × 15 | 15 |
| 5, after appending `A-104,4,9` | 4 × 9 | 36 |

Initial sum: `24 + 21 + 15 = 60`. Four-row sum: `60 + 36 = 96`. A blank Quantity should display a blank result. Leave D3 downward clear so the array can expand.