estimate the force on the flange bolts at section 1

Water flows through the elbow in the figure below and exits to the
atmosphere. The pipe diameter is D1 = 12 cm. while D2 = 4 cm. At a weight
flow rate of 152 N/s, the pressure pl = 2.4 atm (gage). Neglecting the
weight of water and elbow, estimate the force on the flange bolts at section 1