Generate a valid SQL query to extract all customers with a given last name from a customer database.
Last name: Smith
```sql
SELECT * FROM customers WHERE last_name = 'Smith';
```
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate a valid SQL query to extract all customers with a given last name from a customer database.

### Input:
Last name: Smith

### Output:
```sql
SELECT * FROM customers WHERE last_name = 'Smith';
```