$3)$Three objects of equal mass $m_1=m_2=m_3=2\mathrm{.}70kg$ are located on the vertices of an equilateral triangle of length

$d=3\mathrm{.}60m.$ A fourth mass $m_4=15\mathrm{.}5kg$ is at the center of the triangle. What is the net gravitational force on the mass $m_1$

that is at the origin? Express your answer in vector form.

vec$(F{)}_{\text{n}\text{e}\text{t}}=,N$