\\\\(\ extbf{Step 1: Newton's Second Law,}\\\\)From Newton's second law \\\\(F = \\dfrac{dP}{dt}\\\\) \\\\(....(1)\\\\)Where, \\\\(P=mv\\\\) is the momentum \\\\(\ extbf{Step 2: Total bullets fired per sec}\\\\)Let n be the total number of bullets firedThe force exerted by man must balance the change in momentum of the bullets per second. \\\\(\ herefore P = nmv\\\\) \\\\(;\\\\) \\\\(m\\\\) and \\\\(v\\\\) are constant (Given) \\\\(\\Rightarrow F = \\dfrac{d}{dt} (nmv)\\\\) \\\\(\\Rightarrow\\\\) \\\\(\\dfrac{dn}{dt} = \\dfrac{F}{mv} = \\dfrac{144 (N)}{40 \ imes 10^{-3}(kg) \ imes 1200(m/s)} = 3\\\\)Hence total number of bullets fired per second i.e., \\\\(\\dfrac{dn}{dt} = 3\\\\).Hence, Option \\\\(B\\\\) is correct