$15.$ Nick has time, budget and adequate supplies and equipment to finish his project. However,

there is only one trained engineer assigned to the project team. According to his schedule

model, Nick needs at least three engineers. He will need to adjust the start and finish dates

for schedule activities to compensate for this constraint, which is $\_\_\_\_\_\_\_\_\_\_\_\_?$

a$)$ Logical order of activities

b$)$ Activity duration

c$)$ Cash flow concerns