Find the width of central maxima given $\lambda = 5 \times 10^{-5}\;cm$ slit separation $d= 0.15 \;cm$ and distance between screen and slit $D= 2.1 \;m$

Question

$(a)\;0.70\;mm \\ (b)\;1.4 \;mm \\ (c)\;14\;mm \\ (d)\;7\;mm$