Consider the four variables A, B, C and D and a function Z of these variables, $$Z = 15A^2 - 3B^4 + C + 0.5D$$ It is given that A, B, C and D must be non-negative integers and thatall of the following relationships must hold:
i) $$2A + B \leq 2$$
ii) $$4A + 2B + C \leq 12$$
iii) $$3A + 4B + D \leq 15$$
If Z needs to be maximised, then what value must D take?

A

15

B

12

C

0

D

10

E

5