The first unit of a product took 832 hours to build, and the learning curve is 75%. How long will it take to make the 10th unit? (Use at least three decimals in the exponent if you use the logarithmic approach.)

A) less than 250 hours
B) from 251 to 275 hours
C) from 276 to 300 hours
D) from 301 to 325 hours
E) 325 or more hours

The time to produce the nth unit in a learning curve is given by T_n = T_1 * n^(log(b)/log(2)), where T_1 is the time to produce the first unit, n is the unit number, and b is the learning percentage as a decimal. For a 75% learning curve, b = 0.75. Thus, T_10 = 832 * 10^(log(0.75)/log(2)). Calculating this gives T_10 ≈ 320.4 hours, which falls into the range from 301 to 325 hours.