$\text{Shift in position of central maxima along + y axis due to slit of width t is }\Delta y_1 = \frac{(2\mu -1)tD}{d}$

$\text{Shift in position of central maxima along - y axis due to slit of width 2t is }\Delta y_2 = -\frac{(\mu -1)2tD}{d}$

$\text{Net Shift is }\Delta y = y_1 - y_2 = \frac{tD}{d}$