A woman pulls a sled which, together with its load, has a mass of $m$ kg. Let $g$ be the acceleration due to gravity. If her arm makes an angle of $\theta$ with her body (assumed vertical) and the coefficient of friction (a positive constant) is $\mu$, the least force, $F$, she must exert to move the sled is given by $$F={mg\mu\over\sin\theta+\mu\cos\theta}.$$ If $\mu=0.15$, find the maximum and minimum values of $F$ for $0\leq\theta\leq\pi/2$.

maximum force = Newtons
minimum force = Newtons