If number of images formed by two mirrors inclined to each other is 3, what is angle between the mirrors?

Image formed by a plane mirror is

Image formed by a plane mirror is :-

When the image formed by a concave mirror is at infinity then what is the position of the object?

An object is plced at a distance of 25 cm from a shperical mierror and its image is formed behind the mirror at a distance of 5 cm.Find the focal length of the mirror.Is the mirror concave or convex in nature?