Simple two cells check and calculate

Question

I have problems with this formula and cant get it right. I cant use the "IFS" in my excel.

Want I would like to calculate for Cell C1:

If A1 is empty and B1 is empty = 0
If A1 is not empty and B1 is empty = A1
If A1 is empty and B1 is not empty = B1
If A1 is not empty and B1 is not empty = (A1*0,6) + (B1*0,4)

Example for last

A1 = 20 and B1 = 2

= (A1*0,6) + (B1*0,4) 
= 20 *0,6 + 2*0,4 
= 12 + 0,8 
= 12,8

Thank you