Which conventions are followed for spherical mirrors and lens?

Concept:-

New cartesian sign convention for spherical mirrors:

• The object is always placed on the left of the mirror and light from the object falls from the left to the right.
• All distances parallel to the principal axis are measured from the pole.
• All distances measured to the right of the pole are taken as +ve.
• All distances measured to the left of the pole are taken as -ve.
• The height measured upwards perpendicular to the principal axis is taken as +ve.
• The height measured downwards perpendicular to the principal axis is taken as -ve.

EXPLANATION:

• The focus point is in front of the mirror for the concave mirror and behind the mirror for the convex mirror. 
• So, it is positive for convex mirrors and negative for the concave mirror as per the given sign conventions. 
• The correct option is 'f of the concave mirror is negative, and that of a convex mirror is positive'.