Two students push a 20.0\,\text{kg}20.0kg20, point, 0, start text, k, g, end text desk from opposing directions. One student pushes with a force of 5.0\,\text{N}5.0N5, point, 0, start text, N, end text to the left, and the other student pushes with a force of 2.0\,\text{N}2.0N2, point, 0, start text, N, end text to the right. Calculate the horizontal acceleration of the desk.