Expected return on security X is $20\%,$ expected return on security Y is $30\%,$ risk $(\%)$ of security X is $10\%$ and that of Y is $16\%.$ If coefficient of correlation between the returns of X and Y is $-1,0\mathrm{.}5$ and $+1.$ Evaluate the impact on the gains from diversification, if investment is made equally in both the stocks.