X1 = = An electron is fixed in place along the x-axis at the position 10 cm, and a proton is fixed in place along the x-axis at the position X 70 cm. A second proton is placed along the x-axis at the position x3 55 cm and is released from rest. What is the initial acceleration of the proton? The symbolic answer must be written in terms of the quantities X1, X2, X3, C, Mproton, and k, but not all of these may be needed. (Note: you may ignore any gravitational interac- tions in this problem.) =