Answer:
0.2 hours = 12 minutes required to produce the 20th unit
I used an online learning curve calculator to solve this question
40th unit
the time it takes to produce the 40th unit = cumulative time required to produce 40 units - cumulative time required to produce 39 units. Since we are given the time to produce the 20th unit, then we must adjust our formula (12 minutes will be used as the time required to produce 1 unit) ⇒ cumulative time required to produce 20 units - cumulative time required to produce 19 units = 105.940 minutes - 102.479 minutes = 3.461 minutes
80th unit
we will modify all our calculations in the same way as before in order to determine the expected time of the 80th and 160th units:
the time it takes to produce the 80th unit = time required to produce 60 units - time required to produce 59 units = 211.990 minutes - 209.796 = 2.194 minutes
160th unit
the time it takes to produce the 160th unit = time required to produce 140 units - time required to produce 139 units = 356.020 minutes - 354.477 = 1.543 minutes