The three grains are rice, wheat, and corn
Rice is the main grain used in places such as Asia ans SEA, corn is mostly used in the Americas, while wheat is mostly found in European countries.
The Sample Size formula, also known as the Cochran Formula, allows for calculation of an ideal sample size. Below, I have inserted a picture of the formula, where it’s variables are as follows,
N=population size
E= margin of error
Z=z-score
Finding a mate??? I’m not sure