At 700 K, the equilibrium H₂(g) + I₂(g) ⇌ 2 HI(g) has Kc = 55.3. A 1.00 L flask initially at equilibrium contains [H₂] = 0.10 M, [I₂] = 0.10 M, and [HI] = 0.75 M. Without changing the temperature or volume, 0.20 mol of HI(g) is injected into the flask. Calculate the equilibrium concentration of HI after the system re-equilibrates (solve exactly; do not assume the change is negligible).