A binary PUT option will pay $1 if price of underlying at expiration falls below strike price K, and zero otherwise. A binary CALL option will pay $1 if price of underlying expires ABOVE strike price K and zero other wise.

A binary PUT will be priced at the CDF value at strike K. A binary CALL is worth 1 - CDF(K).

Underlying price at $100. Option has 1 year to go b/f expiration.

If you observed $80 PUT is priced at 16 cents. What is the implied volatility in dollar term between now and expiration?