Ethanal vapour goes through thermal decomposition in a chemical reaction C2H4O(g) CH4(g) + CO(g)

This is the graph:

a) Look at the graph find the instantaneous rate of decomposition of CHO when the concentration is 0.200 mol/L at 270 s. Place the tangent line on the curve. b) Determine the initial rate of reaction on the graph then place the tangent line on the curve.

Plot of concentration of ethanal vabor vs time