How to select cell values ​​from a range in excel?

Question

excel

Good afternoon!
I have a table like this in excel:

|     A      | B  |
-------------------
| 01.10.2015 |  5 |
| 02.09.2015 | -3 |
| 12.10.2015 | 20 |

It is necessary in one cell on the adjacent sheet to display the sum of all positive numbers from column B, if the date in column A falls in October. Dates may not be in order. Numbers can be positive or negative. The number of lines is not known in advance.
Can this be done with one formula?

Answer 1

Formula:
For the formula to work, you need to press CTRL + SHIFT + ENTER instead of ENTER (this is how formulas apply to arrays).