The spherical gas tank is fabricated by bolting together two hemispherical thin shells. If the 8 -m inner diameter tank is to be designed to withstand a pressure of \(2 \mathrm{MPa}\), determine the minimum wall thickness of the tank and the minimum number of 25 - \(\mathrm{mm}\)-diameter bolts that must be used to seal it. The tank and the bolts are made from material having an allowable normal stress of \(150 \mathrm{MPa}\) and \(250 \mathrm{MPa}\), respectively.