Chance of a Girl Having a Sister

Given the distribution of the number of children per family as shown in the table below: | n_children | 0 | 1 | 2 | 3 | 4 | >=5 | |------------|----|----|----|----|----|-----| | p | 0.3| 0.25| 0.2| 0.15| 0.1| 0 | Imagine a random girl from this population of children. What is the probability that she has at least one sister?