What is the correct propotion

A radio talk show host is interested in the proportion p of adults in his listening area who think the drinking age should be lowered to eighteen. To make this determination, he poses the following question to his listeners: "Do you think that the drinking age should be reduced to eighteen in light of the fact that eighteen-year-olds are eligible for military service?" He asks listeners to phone in and vote "yes" if they agree the drinking age should be lowered and "no" if not. Of the 200 people who phoned in, 140 answered "yes." The standard error for the proportion pˆ of those who phoned in and answered "yes" is

A. 0.46.
B. 0.032.
C. 0.00105.

I've never heard of this, but from my understanding, if 140 answered yes and 60 answered no, then the standard error of proportion is:

√((140/200)(60/200)/200) = 0.032