Sally's communications business began as a one-person operation, but sally Soon found that she had more work than she could do herself. Although it was not in her plan to hire any subcontractors during the first year, she decided to go ahead and bring in three contractors to work on new projects. At the same time, she decided to increase the contractor's daily fee to $500. In the market for sub-contractors, what is this an example of?

a)Positive supply shift

b)negative demand shift

c)negative supply shift

d)positive demand shift