Solution :
a). The normal form in the game is given below as :
The King
The Enemies Hire Not hire
To Poison (-5, 10-w) (5, 0)
Not to Poison (0, 10-w) (0, 10)
b). For the enemies there is no such dominant strategy and the king also does not have any dominant strategy. Therefore, there is no pure strategy of Nash equilibrium.
c). The backward induction helps to suggest that there is a spine for the game when the king hires a Royal taster and the enemies do not poisons the king : (Hire, Not poison).
d). Yes the king needs to offer a wage that is greater than going wage,
in order to attract the willing taster as the value of the life of his more.