(a) The mean of the masses of a group of four student is 30 kg.
One student joins the group .The mean of the masses of the five students is 32 kg.
Find the mass of the student who joined the group.
(b)The mean of the five articles is 215 g. When another article is added, the mean of the masses of the six articles is 220 g. Find the mass of the sixth article.