Draw a free-body diagram with all four forces: weight, friction, normal force, and external force.
Let's call "eastward" the x-direction and "upward" the y-direction. The external force F has an x- and a y-component, given by F cos(35) and F sin(35), respectively. The x-component is canceled by the force of static friction, Fs, while the y-component, together with the normal force N, is canceled by the weight W of the box:
∑ Fx = F cos(35) - Fs =0
∑ Fy = F sin(35) + N - W =0
The second equation tells us that the normal force is
N = W - F sin(35)
We need the normal force because it is part of the force of friction:
Fs = µ N = µ (W - F sin(35) )
Substitute this into the x-equation:
∑ Fx = F cos(35) - µ (W - F sin(35) ) =0
You could plug in your numbers at this point and solve for F. I prefer first solving for F algebraically before plugging in the values:
F ( cos(35) + µ sin (35)) = µ W
F = µ W /( cos(35) + µ sin (35))
F = 0.4 *150 /(cos (35) + 0.4 sin(35) ), which you can calculate yourself.