Subconvexity for $GL(3)\times GL(2)$ $L$-functions in $t$-aspect

Let $\pi$ be a Hecke-Maass cusp form for $SL(3,\mathbb{Z})$ and $f$ be a holomorphic (or Maass) Hecke form for $SL(2,\mathbb{Z})$. In this paper we prove the following subconvex bound $$L(\frac{1}{2}+it,\pi \times f){\ll }_{\pi ,f,\epsilon }(1+\mathrm{\mid }t\mathrm{\mid }{)}^{\frac{3}{2}-\frac{1}{42}+\epsilon }\mathrm{.}$$