Unit times for a job exhibit a learning effect. If the second unit took 30 hours, and the fourth unit took 21 hours, roughly how many hours would you estimate the third unit took?

The answer is "24 Hours".

Step-by-step explanation:

The calculated time for unit:

Calculating the time for unit:

On dividing the value from equation (a) to (b):

 r= 0.7

Put the value of r into equation (a)  

Calculating the value of time for unit:

i just took the test, the correct answer is .. 31.5 in.