3 George throws two coins, \(A\) and \(B\), at the same time. Coin \(A\) is biased so that the probability of obtaining a head is \(a\). Coin \(B\) is biased so that the probability of obtaining a head is \(b\), where \(\mathrm { b } < \mathrm { a }\). The probability generating function of \(X\), the number of heads obtained by George, is \(\mathrm { G } _ { \mathrm { X } } ( \mathrm { t } )\). The coefficients of \(t\) and \(t ^ { 2 }\) in \(\mathrm { G } _ { \mathrm { X } } ( \mathrm { t } )\) are \(\frac { 5 } { 12 }\) and \(\frac { 1 } { 12 }\) respectively.

1. Find the value of \(a\).
   The random variable \(Y\) is the sum of two independent observations of \(X\).
2. Find the probability generating function of \(Y\), giving your answer as a polynomial in \(t\).
3. Find \(\operatorname { Var } ( Y )\).