One can use FRET to follow the hybridization of two complimentary strands of DNA. When the two strands bind to form a double helix, FRET can occur from the donor to the acceptor, allowing one monitor the kinetics of helix formation (for an example of this technique, see Biochemistry 34 (1995), 285). You are designing an experiment using a FRET pair with R₀ = 59.6 Å. For B-form DNA the length of the helix increases 3.46 Å per residue. If you can accurately measure FRET efficiency down to 0.10, how many residues is the longest piece of DNA that you can study using this FRET pair?