\(u =-10 cm\)

\(v=?\)

as \(\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\)

\(\frac{1}{v}+\left(\frac{1}{-10}\right)=\frac{1}{-4}\)

\(\frac{1}{v}=\frac{1}{10}-\frac{1}{4}\)

\(\frac{1}{v}=\frac{4-10}{40}\)

\(v=\frac{40}{-6}\)

\(V =\frac{-20}{3}\)

\(m =\frac{- V }{ u }\)

\(m=\frac{-\left(-\frac{20}{3}\right)}{-10} \Rightarrow m=\frac{-2}{3}\)

or image will be real, inverted and unmagnified.