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1. [Maximum mark: 4]

The following table shows the number of hours of play time, $x$, and sleep time, $y$, for a group of six children, over the period of one week.

The regression line of $y$ on $x$ for this data can be written in the form $y = ax + b$.

(a) Find the value of $a$ and the value of $b$. [2]

(b) Use the equation of the regression line to estimate the sleep time of a child whose weekly play time is 20 hours. [2]