Question 14

14. [Maximum mark: 6]

A vet wants to find a relationship between the age in days of a breed of puppy ($d$) and its weight in kg ($w$).

To do this he collects a large quantity of data and plots two graphs.

He finds the regression line for each graph. His results are summarized in the table.

Based on these results, find the best of the two possible relationships between $w$ and $d$.

Express your relationship in the form $w = f(d)$ where $f$ is a simplified expression.

Justify your choice of expression.