A farmer grows cotton, maize and wheat on 1 hec, 5 hec and 4 hec of land respectively. The average yields of cotton, maize and wheat per hec on his farm are 4q, 20q and 25q as against State averages of 5q, 10q and 20q for the respective crops. What is the crop-yield index of his farm?

A crop yield index of a farm is a number that denotes the average of the yields of various crops grown on a farm or in a locality to the yields of the same crops on another farm.
It is calculated by dividing the gross cropped area by the net area available on the farm, multiplied by 100.
Here, all the given options are not correct.