A polyethylene balloon at an altitude of 30,000 m is filled with helium gas at a pressure of 10−2 atm and a temperature of 300 K. The balloon has a diameter of 10 m, and has numerous pinholes of diameter 10−5 m each. How many pinholes per square meter of the surface must there be if 1 per cent of the gas were to leak out in 1 hour?