22) D


Mass of PbS in 478kg of ore = 70% of 478 = 0.7 x 478 = 334.6kg ≈ 335 kg
Mr of PbS = 207 + 32 = 239
n = 335/239 ≈ 336/240 = 1.4 moles

Moles of Pb = 1.4 moles
n = m/Mr
m = n x Mr
m = 1.4 x 207 = 289.8

Hence D is the answer.