Multiply of Lasts of two series

I hope you can help me.
I have two series.

  • for currencies
  • for wallet_value

Now I fetch the last of currencies for currency “eur” and I fetch the last of wallet_value.
In the last step I want to multiply both “last”-values; but that is not working. The “last” values are on different “records” so the multiply is 0.
A “distinct” to get both values on the same record is not working.

Anyone has an idea how to manage that ?