With reference to Exercise 7.6 on page 304,
(a) Evaluate s²;
(b) Construct a 99% confidence interval for β₀;
(c) Construct a 99% confidence interval for β₁.

Data From Exercise 7.6

Normal Stress, x        Shear Resistance, y
26.8.......................................26.5
25.4.......................................27.3
28.9.......................................24.2
23.6.......................................27.1
27.7.......................................23.6
23.9.......................................25.9
24.7.......................................26.3
28.1.......................................22.5
26.9.......................................21.7
27.4.......................................21.4
22.6.......................................25.8
25.6.......................................24.9