$($a$)$ Define reaction selectivity and explain why selectivity analysis is important in chemical reactor design and optimizabion?

$[4$ marks$]$

$($b$)$ Reactant A decomposes of $300K$ following three simullaneous reactions Io form $B,x$ and $Y$ as shown in Table $Q4.B$ is the desired product, $x$ and $Y$ are undesired. The leed volumetric flow rate of $A$ is $20L{s}^{-1}$ and concentration of $0\mathrm{.}4$ mol. $L^4$

Table Q$4.$ The parallei reactions and parameter values.

$\backslash$table$[[$No$,$Reaction,$\backslash$table$[[$Reaction$],[$Order$]],\backslash$table$[[$Rate Constant$],[($al $300K)]],\backslash$table$[[$Activation Energy$],[($k$.$J$.$mar'$)]]],[1,A{k}_{1}x,0^{hh}$ order,$\backslash$table$[[k_1=1\mathrm{.}0{10}_1^{-1}mol{L}^{-1}*s^{-1}$