Assuming the normality assumption is valid, test ????0 ∶ ????1 = 0 versus ???????? ∶ ????1 ≠ 0 at the ???? = 0.05 level when

(a) ˆ????1 = 0.61, ????????(ˆ????1) = 0.34, and ???? = 60.

(b) ˆ????1 = −4.54, ????????(ˆ????1) = 1.12, and ???? = 60.

(c) ˆ????1 = −4.54, ????????(ˆ????1) = 2.67, and ???? = 0.109.

(d) ˆ????1 = 9.83, ????????(ˆ????1) = 1.12, and ???? = 0.000.