signal analysis - Fundamental frequency

Can someone help me:

I have a signal which consist of three frequencies; for example, $f_1=800\,\text{Hz}$, $f_2=1050\,\text{Hz}$, $f_3=1600\,\text{Hz}$. How can i compute the fundamental frequency?

Also, is there a method called "frequency histogram method" which is used to compute fundamental frequency? Can someone explain it to me?

Thanks.