Make a graph of the data given in the refraction ,identify the number of layers, calculate critical distance, velocity and layer thickness.

X = 2,4,6,8,10,12,14,16,18,20,22 ,24

T=0.005,0.011,0.014,0.020,0.025.0.028,0.031,0.033,0.034,0.036,0.037,0.039