Assume the lifetime (in months) of batteries is modeled as an exponential random variable with parameter 𝜆 . The probability density function of the random variable is 𝑝 𝜆 ( 𝑥 ) = 𝜆 𝑒 − 𝜆 𝑥 , with 𝑥 ∈ [ 0 , ∞ ) . We have collected an i.i.d. sample of 3 batteries whose lifetimes in months are 8, 10, 9, respectively. The standardized log-likelihood of a sample with 𝑛 i.i.d. observations is 1 𝑛 log 𝐿 ( 𝑥 , 𝜆 ) = 1 𝑛 ∑ 𝑖 = 1 𝑛 ( log ( 𝜆 ) − 𝜆 𝑥 𝑖 ) . Given this information what is the Maximum Likelihood estimate of 𝜆 ? 单项选择题