Assume an 80% Learning Curve and That the First Unit

Multiple Choice

Assume an 80% learning curve and that the first unit takes 6 hours. How long does it take to produce the second unit? Use the following values as needed to respond:
Ln(95%) / ln(2) = -0.074
Ln(90%) / ln(2) = -0.152
Ln(85%) / ln(2) = -0.234
Ln(80%) / ln(2) = -0.322
Ln(75%) / ln(2) = -0.415
Ln(70%) / ln(2) = -0.515

A) 4) 1 hours
B) 3) 6 hours
C) 4) 8 hours
D) Some other amount