The Baire classification of strongly separately continuous functions on $\ell_\infty$
We prove that for any $α\in[0,ω_1)$ there exists a strongly separately continuous function $f:\ell_\infty\to [0,1]$ such that $f$ belongs to the $(α+1)$'th /$(α+2)$'th/ Baire class and does not belong to the $α$'th Baire class if $α$ is finite /infinite/.