The figure shows a double cast-iron bearing block that is to be bolted permanently to a steel ceiling joist. One steel washer is used under each bolt head and nut. The diameter of the washer face is 50% greater than either the nut or the bolt diameter. Other details provided in the table. Ceiling joist Double bearing block Washer 20 mm Thickness 20 mm 20 mm 3.4 mm Material Steel Cast iron Steel Celling Jolst Calculated stiffness 10,000 MN/m 6,000 MN/m 40,000 MN/m 20 mm Double Bearing-Block W/2 W/2 Using the given data, the member stiffness for the joint (k) is (select the closest number): (a) 1050 MN/m (b) 2150 MN/m (c) 3157 MN/m (d) 4156 MN/m