Answer:
18.50 minutes
Step-by-step explanation:
cutting and drying/styling
= 20 + 10 = 30 minutes
percentage = 35%
= 30 * 0.35 = 10.50
coloring and styling/drying
= 10 + 10 = 20 minutes
percentage = 15 percent
0.15 * 20 = 3.00
only dryind and styling
time = 10 minutes
probability = 1 - 0.15+0.35 = 0.50
0.50 * 10 = 5.00
the expected activity time for this process = 10.50 + 5.00 + 3.00
= 18.50