Answer:
The correct answer is $5.83.
Explanation:
According to the scenario, the given data are as follows:
Cost for 1st unit (C1) = $10
Learning rate (LR) = 0.9
So, we can find the unit cost for 35th unit by using logarithmic approach as follows:
 =
 = 
Where,  = C is for cost and N is for number of unit
 = C is for cost and N is for number of unit
 = Cost of 1st unit
 = Cost of 1st unit
 = N is for number of unit and b is for slope of learning curve.
 = N is for number of unit and b is for slope of learning curve.
So, b = (Log of the learning rate) / (Log 2)
So, by putting the value, we get
 = $10 ×
 = $10 × 
= $10 × 0.583 
= $5.83
Hence, the unit cost for the 35th unit will be $5.83.