#### Answer

a)0.6
b)We have to have n-1 values determined which determines the nth value.

#### Work Step by Step

a)The mean is 0.62, therefore the sum of the values is: $5\cdot0.62=3.1$. The sum of the values we know is: 0.3+0.4+1.1+0.7=2.5, therefore the missing value is: 3.1-2.5=0.6.
b)We have to have n-1 values determined which determines the nth value. n-2 values would not be enough because then we would only know the sum of the remaining two.