Answer:
4.428 hours
Step-by-step explanation:
If the learning rate is 0.81, the slope of the learning curve is:
[tex]b=\frac{ln(0.81)}{ln(2)} \\b=-0.304[/tex]
The time it takes to produce the n-th unit is:
[tex]T_n=T_1*n^b[/tex]
If T1 = 8 hours, the time required to produce the seventh unit will be:
[tex]T_n=8*7^{-0.304}\\T_n=4.428\ hours[/tex]
It will take roughly 4.428 hours.