Please help, didn’t study, quiz is timed

Initially, the balloon had 3.0 liters of gas at a pressure of 400 kpa and was at a temperature of 294 k. if the balloon is cooled to 277 k and its volume decreased to 1 l, what will the new pressure in the balloon be?

Which of these properties, used alone, would be least useful in identifying most minerals? a. color b. luster c. streak d. density

Ineed ! i have no clue how to do this problem.