the polynomial x^3 - 4x^2 + 5x - 1 = 0 has 3 roots a,b and y

i. find the value of a + b + y

ii. find the value of aby

iii. find the equation of the polynomial with roots 2a, 2b and 2y

i got 4 for i and 1 for ii

are these right??

how do you do iii.?