"Calculate the total pressure of mixture of 1.05g of nitrogen gas, 3.66g of hydrogen gas, and 2.16g of chloring gas mixed in a sealed 3.6L container at 19°C"

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?