a)
α1 = tan^{-1}(0.12) = 6.84°
α2 = tan^{-1}(0.13) = 7.41°
α3 = tan^{-1}(0.10) = 5.71°
α4 = tan^{-1}(0.11) = 6.28°
b)
h1 = 1.2 * 0.12 / √(0.12^2 + 1) = 0.1430
h2 = 1.2 * 0.13 / √(0.13^2 + 1) = 0.1547
h3 = 1.2 * 0.10 / √(0.10^2 + 1) = 0.1194
h4 = 1.2 * 0.11 / √(0.11^2 + 1) = 0.1312