Consider the procedure described in Section 9.3 for estimating average delay d_i. Suppose that u = 0.1. Let r₁ – t₁ be the most recent sample delay, let r₂ – t₂ be the next most recent sample delay, and so on. 

a. For a given audio application suppose four packets have arrived at the receiver with sample delays r₄ – t₄, r₃ – t₃, r₂ – t₂, and r₁ – t₁. Express the estimate of delay d in terms of the four samples. 

b. Generalize your formula for n sample delays. 

c. For the formula in part (b), let n approach infinity and, give the resulting formula. Comment on why this averaging procedure is called an exponential moving average.