450. A sample of size $n=50$ has been drawn from the population:

| variant | $x_{i}$ | 2 | 5 | 7 | 10 |
| :--- | :--- | ---: | ---: | ---: | ---: |
| frequency | $n_{i}$ | 16 | 12 | 8 | 14 |

Find the unbiased estimate of the population mean.