A direct time study was taken on a manual work element using the snapback method. The regular cycle consisted of elements, a, b, c and d. Element d is an irregular element performed every four cycles.

Work element a b c d

Observed time (min) 1.56 1.25 2.50 1.35

Performance rating 100% 90% 110% 85%

Determine the Normal time for the cycle. Select correct answer from below:

1. 1.64 min

2. 5.72 min

3. 6.58 min

4. 7.56 min