The right answer is 20 aminoacids per second.
Transcription is a mechanism for synthesizing RNA from DNA.
Translation is a mechanism for synthesizing a polypeptide sequence from mRNA by converting the nucleotide triplet (codons) to amino acids.
So if one amino acid corresponds to three nucleotides. The polypeptide synthesis rate should be 20 amino acids per second for 60 nucleotides per second.
3 nucleotides ==> 1 amino acid
60 nucleotides ==> 60/3 = 20 amino acids.