need help please

Two point charges Q, =-5.1nC and Q, = 8.7nC are placed at the corners of an equilateral triangle as shown in the figure below. The side length of the triangle is a= 0.83m. Determine the magnitude of the electric field at the empty corner of the triangle. Express your answer using one decimal place in units of N/C. Please note that the charges are given in units of nano coulombs. Take Coulomb's constant as k = 9.0x 109 N . m2/C2. y Q1 a a Q2 a