explain please

Consider the isosceles triangle shown below. If the electric potential at the empty corner due to the two charges, Q, and Q , is 10.8 volts, how much work is required to bring a third charge, @ = 2.9C. from infinitely far away to the empty corner? Express your answer in units of Joules using one decimal place. Note: Do not forget the minus sign, if your answer is negative. y Q1 a a X Q2 b