No saying anyone would do this, since I think the dollars days are numbered, but an interesting mathematical exercise.
Of course, this number assumes no overheads in the transactions etc. so would be less, but still.
Start: $100,000
$1 = 83.59R
$100,000 = 8,359,000R
Fixed price for Gold in Rubles = 5000/g
8,359,000/5000 = 1,671.8g of Gold
Spot price for gold $62.52/g
1671.8g * $62.52 = $104,520.94
That's a 4.52% gain.
Equilibrium would be an exchange rate of $1 = 80R