The average weight across 50 staff members is given as 'z' kg. When one among them, who has been replaced by a new joiner who weighs 70 kg, the overall average weight has decreased to 'z - 1' kg. After that, when this new employee is again replaced by an officer, the average weight then increases to 'z + 0.6' kg. Can you determine the average weight of the officer and the original staff member who was initially substituted?