tan dip = Z/H
H = T cos dip
therefore (tan dip x cos dip) = Z/T
since tan x cos = sin,
sin dip = Z/T; dip = arcsin 0.5921 = 36.3
H = 76 x cos 36.3 = 61.2
So I would say that a) is indeed the correct answer - although I have no idea what the subject is about. Just basic trigonometry and algebra - it is the wont of the JAA to ask rather pointless questions....and answer d) is a deliberate ploy to ensure you RTFQ!