A solid adsorbent is used to remove colored impurity from an aqueous solution. The original value of color on an arbitrary scale is 48. It is required to reduce this to 10 % of its original value Using the following data find the number of stages needed for 1000 kg of a solution in a counter current operation if 1.5 times the minimum adsorbent is used.

kg of adsorbent/kg of solution	0	0.001	0.004	0.008	0.02	0.04
Equilibrium color	48	43	31.5	21.5	8.5	3.5

Solve the problem and make a graph.