Answer: 174
Step-by-step explanation:
Negating the fact that mature mRNA contains a 5' cap and Poly-A tail we will simply divide the number of bases by 3.
Three bases make up a codon and each codon encodes for a single amino acid. Mature mRNA does not contain any introns so the bases within are exons and are protein encoding.
522/3 = 174 amino acids