[填空题]
A tank contains 26.0 m7 2( fjdcpdplxe42zr*4 fdg /xyal)/koz 7zry,bnfn4 +52xjpg of $O_2$ gas at a gauge pressure of 8.70 atm. If the oxygen is replaced by helium, how many kilograms of the latter will be needed to produce a gauge pressure of 7.00 atm? kg He