need help to understand the problem

Market Share The following figure shows the devastating effect the opening of a new discount department store had on an established department store in a small town. The revenue of the discount store at time t (in months) is given by f(t) million dollars, whereas the revenue of the established department store at time t is given by g(t) million dollars. Answer the following questions by giving the value of t at which the specified event took place. y =g(1) y = f(1) (a) The revenue of the established department store is decreasing at the slowest rate. t = (b) The revenue of the established department store is decreasing at the fastest rate. O t1 Otz Ot3 (c) The revenue of the discount store first overtakes that of the established store. Ot1 O t2 Ot 3 (d) The revenue of the discount store is increasing at the fastest rate. Ot, Ot3