Answer:
1.9393 hours
Explanation:
In general, if the learning curve is p%, then the time
estimated to produce the nth unit is given by the logarithmic curve

where
is the time needed to produce unit 1
and b is given by
(slope of the learning curve)
In our case

So we must find

We know that the cumulative average labor hours to assemble the first five units of product A was 15.962 hours, hence

applying the formula,

factorizing

computing the terms we have

Finally, to compute the time estimated to produce the 21st unit, we replace in the formula with n=21
