Binomial Theorem - Coefficients in Products of Binomial Expansions

Given that the coefficient of \({{x}^{2}}\) in the expansion of \({{\left( 1-3x \right)}^{3}}{{\left( 1+px \right)}^{6}}\) is \(\frac{221}{12}\), find the possible values of the constant \(p\).

Hence, find the coefficient of \({{x}^{2}}\) in the expansion of \({{\left( 1-3x \right)}^{3}}{{\left( 1+6px \right)}^{6}}\) for \(0 < p < 1\).