Find the distance of the image when an object

Find the distance of the image when an object is placed on the principal axis at a distance of 10 cm infront of a concave mirror whose radius of curvature is 8 cm.

Radius of curvature ® = 8 cm
Focal length f = R/2 = 8/2 = 4 cm
Object distance (u) = 10 cm
Image distance (v) = ?
We know that mirror formula
1/f = 1/u + 1/v ====> 1/4 = 1/10 + 1/v
====>1/v = 1/4 - 1/10 =5-2/20 = 3/20
v = 20 /3 cm