Question

Polonium-210, a naturally occurring radioisotope, is an α emitter, with t1/2 = 138 d. Assume that a sample of 210^Po with a mass of 0.710 mg was placed in a 230.0 mL flask, which was evacuated, sealed, and allowed to sit undisturbed. What would the pressure be inside the flask (in mmHg) at 20 ∘C after 369 days if all the α particles emitted had become helium atoms? Please answer in mmHg, thank you.