Losses come from an equally weighted mixture of an exponential distribution with mean m1, and an exponential distribution with mean m2. Determine the least upper bound for the coefficient of variation of this distribution.
a.1 b. square root of 2 c. square root of 3. d. 2 e. square root of 5

看不懂解答為何考慮m1或m2=0,假設如m1=0,1/m1不就無法定義了嗎？謝謝各位！！