You are running a series of similar projects and consider that you can use the learning curve approach to estimate the individual project durations? You calculated the time requirements for the first project (T1) as 2000 hours and the time requirements for the second project (T2) as 1800 hours. What is the time requirements for the fourth project (T4)? a) 1692 b) 1620 c) 1600 d) 1400 e) None of the above is correct