Royal Tree Service Has Been Hired to Clear an Area $x$

Essay

Royal Tree Service has been hired to clear an area of trees. If $x$ represents the number of hours they will work, where $x>0$ , then the function defined by $f(x)=125 \llbracket x \rrbracket+250$ gives the total cost in dollars.
(a) Using dot mode and the window $[0,10]$ by $[0,1500]$ , graph this function on a graphing calculator.
(b) Use the graph to find the cost of a 7.5 hour workday.