Simulating births

A health worker wants to see how close real counts come to one half. You will write a function that gives the child for a sperm, simulate many births, and find the fraction of girls. The program then draws a bar chart.

The idea. The egg always carries an X. A sperm carries X or Y with equal chances. X with X gives a girl; X with Y gives a boy.

Your tasks.

1. In child, return "girl" if sperm is "X", and "boy" if it is "Y".
2. Set children to the list of children for every sperm in sperms, in order.
3. Set girls to the number of girls in children.
4. Set fraction to the fraction of girls, rounded to two decimal places.