A variable force $F$ starts acting on a block of mass $5 \mathrm{~kg}$ resting on a smooth horizontal surface. $F$ is varying with displacement $x$ as shown in $F-x$ curve. The velocity of body when its displacement is $3 \mathrm{~m}$ will be
(A) $2 \mathrm{~ms}^{-1}$
(B) $2 \sqrt{2} \mathrm{~ms}^{-1}$
(C) $2 \sqrt{3} \mathrm{~ms}^{-1}$
(D) $6 \mathrm{~ms}^{-1}$