Wires W1 and W2 are made of same material having the breaking stress of 1.25 $\times$ 109 N/m2. W1 and W2 have cross-sectional area of 8 $\times$ 10 $-$ 7 m2 and 4 $\times$ 10 $-$ 7 m2, respectively. Masses of 20 kg and 10 kg hang from them as shown in the figure. The maximum mass that can be placed in the pan without breaking the wires is $\underline{\hspace{2cm}}$ kg. (Use g = 10 m/s2)