What kind of mirror-concave, convex or plane-would be best suited for use in a solar cooker? Why?

A concave mirror reflector would be best suited for use in a solar cooker. This is because a concave mirror is a converging mirror which converges all the light falling on it. It converges a large amount of sun's heat rays onto the required area of cooking holder. A plane mirror does not converge all the light therefore, concave is used. And convex mirror reflector is a diverging mirror so it is also not used.