Answer:
The value is
![w = 6.7 \%](https://img.qammunity.org/2021/formulas/mathematics/college/a6rkguxz5o2a5cbkz1dql2xtfzj7rh7upv.png)
Explanation:
Generally the productivity rate is mathematically represented as
![P_r = K * Z](https://img.qammunity.org/2021/formulas/mathematics/college/zwrr599kwoqaq7skys2t91ka6ok96e3978.png)
Here K is the ha the farmer could harvest in an hour and Z is a typical yield of corn in kg/ha
Now considering 1970
The productivity rate is
![P_r = 0.75 *5000](https://img.qammunity.org/2021/formulas/mathematics/college/oqb4lbsf2wf0zawr0po8o2k3byzxwbh2uf.png)
=>
Now considering 1940
The productivity rate is given as
Generally the productivity ratio is mathematically ration is mathematically represented as
![w = (P_R)/(P_r) * 100](https://img.qammunity.org/2021/formulas/mathematics/college/bsxii5h86hgrdf4wvzv2aailno9nm8x66r.png)
=>
![w = (250)/(3750) * 100](https://img.qammunity.org/2021/formulas/mathematics/college/c9ha1qdppua467y3n03zqlivt0o9tqjp6w.png)
=>
![w = 6.7 \%](https://img.qammunity.org/2021/formulas/mathematics/college/a6rkguxz5o2a5cbkz1dql2xtfzj7rh7upv.png)