Your answer depends on the origin location of the letter and its ultimate destination. If your point of origin is in the United States, you can review USPS postal rates, below.
Otherwise, you can find local postal rates at your local post office.
36 fl oz is 1064.65mL
how many first class stamps does it take to mail a 4 oz letter and package
how many stamps for a 3.4oz envelope
2
27
2.4
36
36 g = 1.27 oz
36 ounces = 2.25 pounds
78 cents
There are 2.25 pounds in 36 ounces.
-2 and 1/2