The sun (diameter d ) subtends an angle $\theta$ radian at the pole of a concave mirror of focal length f. What is the diameter of the image of the sun formed by the mirror ?

Question

$\begin{array}{1 1} d= \large\frac{\theta}{f} \\ d= \large\frac{f}{\theta} \\ d= \theta f \\ none\;of\;the\;above \end{array}$