As stated in the text, the Sun radiates 3.91×1026 joules per second, and thus its mass diminishes by about 4.34×109 kg each second. (a) If you had a cube of water whose mass was equal to 4.34×109 kg, what would be the length of one side of the cube, in km? Assume a density of 1000 kg/m3. (b) The mass of the Sun is 1.99×1030 kg. Calculate how long the sun would last, in years, if it were to keep radiating at its present power level until all its mass is gone.