Various doses of a poisonous substance were given to groups of 25 mice and the following results were observed:
![](https://test.transtutors.com/qimg/7dfba48a-a0b3-41e8-91d2-a637865b1cf7.png)
(a) Find the equation of the least squares line fit to these data.
(b) Estimate the number of deaths in a group of 25 mice that receive a 7-milligram dose of this poison.