As morning sunlight falls on a tethered helium balloon, it expands from a volume of 1.05 ×103 m3 to 1.15 ×103 m3. How much work does the helium do on its environment (assuming the gas bag remains slack)? If the initial temperature of the helium is 270K, how many moles of gas are in the balloon? how much does the helium's internal energy increase? how many joules of solar energy are absorbed?