S box in example 3.1 attached

3.14 Suppose that the S-box of Example 3.I is replaced by the S-box defined by uhe following substitution 011121314151617181914 | B | C | D | E | F TS (z) 8421C63 DA5E7 F90 (a) Compute the table of values NI, for this S-box (b) Find a linear approximation using three active S-boxes, and use the piling-up lemma to estimate the bias of the random variable