Laws Of Motion

A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force $\mathrm{F}=20 \mathrm{~N}$ acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take $\mathrm{g} \simeq 10 \mathrm{~ms}^{-2}$ )