An object with mass m on a horizontal frictionless surface is attached to one end of a horizontal spring with the other end of the spring being attached to a rigid wall. Force is momentarily applied and the mass is set in motion moving in horizontal simple harmonic motion. If the spring constant of the spring is $45$N$/$m and the spring is stretched $-\mathrm{.}88$m when the object is accelerating at $1\mathrm{.}4$m$/$s$^2.$ What is the mass of the object $?$