A position-time graph for a particle moving

A position-time graph for a particle moving along the x axis is shown in Figure P2.7.
(a) Find the average velocity in the time interval t = 1.50 s to t = 4.00 s

(b) Determine the instantaneous velocity at t = 2.00 s by measuring the slope of the tangent line shown in the graph
(c) At what value of t is the velocity zero?