The answer is true, is called Thermal pollotion:).
Answer:
1302 K or 1029 C
Explanation:
Air at atmospheric pressure has pressure of 1 atm
20 C = 20 + 273 = 293 K
Assume ideal gas, according to the ideal gas law:

Where P1, V1 and T1 are the pressure, volume and temperature of the gas before the compression and P2, V2 and T2 are the pressure, volume and temperature of the gas after the compression

Since the gas is compressed to 1/9 of its original volume, V2/V1 = 1/9:
or 1029 C
The gravitational acceleration experienced by the bullet due to the earth's gravitational force is approximately equals to 9.81 m/s^2
At maximum point of height, vertical component of velocity equals to zero because it experiences a pause momentarily before coming back down.
Since -acceleration=(Final velocity-initial velocity) divided by time. Taking upwards to be positive, time taken= 10s