I'm trying to figure out the answer but i'm getting nowhere. me understand how to calculate it.

You don't need to pay attention to the area in this case. We are trying to figure out the mass. What do we need? F= m*a (Force= mass * acceleration of gravity). acceleration of gravity on earth: 9.81m/s^2. so 15000= m*9.81. We need m (Mass) so m= 15000N/ 9.81m/s^2 = 1529.051988 ≈ 1529.05kg.
the mass of the empty plane is therefore 1529.05kg

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.