I understand what the answer explains, but I am confused that, is a bond "that is putable at t=4" equal to a 4-year bond that is putable? Statement 1 says, (1) is a bond putable at t=4, I thought it meant the bond can only be put at or after t=4. Statement (2) is a 4 year bond that is callable. According to the answer, with put-call parity, the value of the bond in statement (2) is equal to that of a 4 year bond that is putable. However, does that mean the bond can be put any time within 4 years?
If so, how can the value of statement (1) and (2) be the same? Or is it that the time to put the bond does not matter when valuing a bond?