A mass $\mathrm{M}$ is suspended by a rope from rigid support at $\mathrm{A}$ as shown in the figure. Another rope is tied at the end $\mathrm{B}$ and it is pulled horizontally with a force $\mathrm{F}$. If the rope $\mathrm{AB}$ makes an angle $\mathrm{\theta }$ with the vertical, then the tension in the string $\mathrm{AB}$ is