Certain Cuntz semigroup properties of extension C*-algebras

Let $0 \xrightarrow{}I \xrightarrow{ } A \xrightarrow{ }A/I \xrightarrow{} 0$ be a short exact sequence of C*-algebras. In this paper, we prove that if $\dim({\rm Cu}(I))\leq n$ and $\dim({\rm Cu}(A/I))\leq m$, then $\dim({\rm Cu}(A))\leq n+m+1$, this result gives an affirmative answer to a problem