We have a table with values like this:

I need a formula for cell D1 to count rows that have in column A value "one" and column B is not empty. For example:
- in first row
A1==onebutB1is empty; (that doesn't count) - in second row
A2==oneandB2is not empty; (that counts 1) - ...
- in 4th row
A4is not equal to value "one" (that doesn't count)
I know about formulas like COUNTIF and COUNTIFS but I can`t figure out how to use them with combined condition.