5. The bubble chart shows the change of the variable "charges" based on the change of the variables including "children", "smoker", and "age".

Summarise three facts based on your interpretation of this bubble chart.

Some note to consider: "charges" is a numerical variable, denoting the insurance fee of a customer; "children" is a numerical variable, denoting the number of children that a customer has; "smoker" is a categorical variable, denoting whether a customer smokes or not; "age" is a numerical variable, denoting age of a customer.