The sun subtends an angle $\alpha=0.5^{\circ}$ at the pole of a concave mirror. The radius of curvature of concave mirror is $R(=1.5 \mathrm{~m}) .$ The size of image formed by the concave mirror is :
(a) $0.785 \mathrm{~cm}$
(b) $0.654 \mathrm{~cm}$
(c) $0.755 \mathrm{~cm}$
(d) $0.622 \mathrm{~cm}$