Protein Synthesis: Energy cost

[Tames]

1. Assume that a particular microorganism has 50 distinct t-rna molecules, and that it has 100 copies of each type of t-rna. Further assume that average number of nucleotides in each t-rna is 80. What is the energy cost, expressed as number of phosphoric anhydride bonds destroyed during the synthesis, to synthesize these 100 copies of these 50 different t-rna molecules?

This is what I did, I'm not sure it's right: ATP's, 2 per amino acid in the polypeptide (100); GTP's, 1 per initiation event (1) and 3 per subsequent amino acid (150) =251 all together, do I convert this to kcal/mol?