Answer
$ \theta = 22.4 ^{\circ}$
Work Step by Step
For this to happen, we need the force in the downward direction to be $3.7m/s^2$
We know that:
$g_{mars}=g_{earth}sin( \theta)$
This gives:
$\theta = sin^{-1}( \frac{g_{mars}}{g_{earth}})=sin^{-1}( .378)$
$ \theta = 22.4 ^{\circ}$
