Consider a battery whose voltage is a random variable with a variance of 1. Two independent measurements of the voltage are taken to estimate the voltage, the first with a variance of 1, and the second with a variance of 4. a) Write the weighted least squares voltage estimate in terms of the initial estimate 30 and the two measurements y1 and y2. b) If weighted least squares is used to estimate the voltage, what is the variance of voltage estimate after the first measurement