What is the domain? What is the range?

Domain means first value whereas range means the second value.. for example:(3,0) . 3 is domain 0 is range..Domain means all the input value that are form on the x axis of graph where as range means all the input value that are form on the y axis.

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50