A vaccine, when it is administered to an individual, produces no side effects with probability 54, mild side effects with probability 152 and severe side effects with probability 151. Assume that the development of side effects is independent across individuals. The vaccine was administered to 1000 randomly selected individuals. If X1 denotes the number of individuals who developed mild side effects and X2 denotes the number of individuals who developed severe side effects, then the coefficient of variation of X1 + X2 equals __________ (round off to 2 decimal places)