Chemisty molar mass and density HELP PLEASE!!

What is the molar mass of a gas with density 0.7 g/L at 770 torr and 40 degrees C? Thanks so much!

D = 0.7 (g/L)
R = 0.0821 (L.atm/mol.K)
T = degree C + 273.15....=> T = 40 + 273.15 = 313.15K
P (1 atm = 760 torr or 760 mmHg) => P = 770/760 = 1.013 (atm)
Molar mass = (Density x R x T) / P
=> Molar mass = (0.7 x 0.0821 x 313.15) / 1.013 = 17.765 (g/mol) ~ 17.77 (g/mol)