Use the ideal gas law:
PV=nRT
p = pressure
v = volume
n = number of moles of sample
R = ideal gas constant = ~0.08206 (l*atm)/(K*mole)
T = Temp in Kelvin
Now we substitute while simultaneously solving for P(pressure)
P = (nRT)/V
P = (2.50 * 0.08206 * (27+273.15)) / 50
P = Now it's your turn.