Answer: if we call P1 to the productivity of the first year, P2 for the second, and so on, then:
1 ) P2 - P1 = 350,000
2) P3 = 2*P2
and P3 = 806,000
now we can put this value on the equation 2, and obtain the value of P2
then P2 = P3/2 = 806,000/2 = 403,000
now we can put this value on equation 1, and obtain the value of P1.
P2 - P1 = 403,000 - P1 = 350,000
P1 = 403,000 - 350,000 = 53,000
So the productivity in the first year is 53,000 units.