Direct shear stress in MPa in the most heavily loaded rivet is

Question

A bracket shown in fig. is rigidly mounted on wall using four rivets. Each rivet is 6 mm in diameter and has an effective length of 12 mm.                                                            

 

Direct shear stress in MPa in the most heavily loaded rivet is

      (a) 4.4                                                                 (b) 8.8

      (c) 17.6                                                               (d) 35.2