Here, radius of each rivet,
`r=0.2 cn = 2 xx 10^(-3) m`
Maximum shear stress, `S_(max) = 5 xx 10^(8) Nm^(-2)`,
Required force F = shear stress `xx` area of cross-section of two rivets
`=(5 xx 10^(8)) xx 2 xx pi xx ( 2 xx 10^(-3))^(2)`
`1.26 xx 10^(4)N`.