Suppose that a particle starts at the origin of the real line and moves along the line in jumps of one unit. For each jump, the probability is $\displaystyle p \ (0\leq p \leq1)$ that the particle will jump one unit to the left and the probability is $\displaystyle 1-p$ that the particle will jump one unit to the right. Find the expected value of the position of the particle after $\displaystyle n$ jumps.