Consider the following diagram for the equilibrium:

$N_2{O}_{4(s)}2N{O}_{2(g)},H=+59kJ$

a$)$ Calculate the value of $K_{eq}$ at $t_1.$

$(1$ mark$)$

b$)$ Calculate the value of $K_{eq}$ at $t_3.$

$(1$ mark$)$

c$)$ What stress was applied at time $t_2?$ Explain.

$(2$ marks$)$