Hey there mate :)
Even if two persons are given the same work load, the speed of the work done gets different by the energy of those persons.
No one is sure that he/she can complete the work within the time. He may or may not.
Also, the physical characteristics makes the work different. If one person has so much power to work all day, the other person may not have.
Therefore, <em>even if two persons do the same amount of work , they may have different power</em><em>.</em>
1) Focal length
We can find the focal length of the mirror by using the mirror equation:

(1)
where
f is the focal length

is the distance of the object from the mirror

is the distance of the image from the mirror
In this case,

, while

(the distance of the image should be taken as negative, because the image is to the right (behind) of the mirror, so it is virtual). If we use these data inside (1), we find the focal length of the mirror:

from which we find

2) The mirror is convex: in fact, for the sign convention, a concave mirror has positive focal length while a convex mirror has negative focal length. In this case, the focal length is negative, so the mirror is convex.
3) The image is virtual, because it is behind the mirror and in fact we have taken its distance from the mirror as negative.
4) The radius of curvature of a mirror is twice its focal length, so for the mirror in our problem the radius of curvature is:
The answer is A.
p=m/v
p= 240/60
p= 4 g/cm^3
B: Extension Lines! You could have just searched this up on google