Anfis for predicting tool wear

can someone help me answer this question please. i have 4 inputs and 1 ouput. all my inputs have 2 level. (inputs= cutting speed(140,160), feed rate (0.15,0.2),depth of cut (0.2,0.4),, I-kaz coef (varies numbers) and output= tool wear measurement (varies number)) can i know what number of membership function for input and output suitable for my problem? which one is suitable, linear or constant output membership function)? please someone help me. i want to predict tool wear using 4 inputs using Anfis.